[Solved] java.lang.NullPointerException in Integrator module

At step 6, integrate, the processing stops with :

-------------------------------- 
Encountered error in module: Integrator 
Error message: java.lang.NullPointerException 
Cause: null 
pj.a(Unknown Source) 
pj.a(Unknown Source) 
pj.doInBackground(Unknown Source) 
javax.swing.SwingWorker$1.call(SwingWorker.java:295)
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Not sure if this helps debugging but the Console shows :

21:59:47 - PROJECTION: reference frame found: M_104_Light_Lum_300_secs_2020-04-25T00-33-27_013.fits
21:59:47 - PROJECTION: regstration model : projective
21:59:47 - PROJECTION: method : rectilinearProjection
21:59:47 - PROJECTION: reference frame width : 4656
21:59:47 - PROJECTION: reference frame height: 3520
21:59:47 - PROJECTION: rotating projection with angle : 0 degrees clockwise
21:59:50 - 2) CALIBRATE: VERIFY CALIBRATION MASTERS: all frames are verified
21:59:50 - FRAME DETAILS UPDATER: starting...
21:59:50 - FRAME DETAILS UPDATER: no new frames to add
21:59:50 - FRAME DETAILS UPDATER: rebuilding all frame details...
21:59:50 - FRAME DETAILS UPDATER: checking if frames were identified earlier...
21:59:50 - FRAME DETAILS UPDATER: updated succesfully
21:59:50 - CONSTRUCT FRAME DETAILS LIST: starting...
21:59:50 - CONSTRUCT FRAME DETAILS LIST: sorting frames...
21:59:50 - CONSTRUCT FRAME DETAILS LIST: Fixing file arrays...
21:59:50 - CONSTRUCT FRAME DETAILS LIST: numbering frames...
21:59:50 - CONSTRUCT FRAME DETAILS LIST: adding frame marks...
21:59:50 - CONSTRUCT FRAME DETAILS LIST: finished
21:59:50 - 6) INTEGRATE: detected a mosaic integration
21:59:50 - 2) CALIBRATE: trying to find calibration details of light frame: /home/hans/astro/data-ssd/M104/Light/Lum/M_104_Light_Lum_300_secs_2020-04-25T00-33-27_013.fits
21:59:50 - 2) CALIBRATE: found calibration masters for light frame: /home/hans/astro/data-ssd/M104/Light/Lum/M_104_Light_Lum_300_secs_2020-04-25T00-33-27_013.fits
21:59:50 - 2) CALIBRATE: Master Dark : /home/hans/astro/data-ssd/Dark-300s/Dark-50x300s-lfh2.fit
21:59:50 - 2) CALIBRATE: Master Flat : /home/hans/astro/data-ssd/Flat/20181013-Lum_flat-integration.fits
21:59:50 - 
21:59:50 - 6) INTEGRATE: loading the reference frame to get a possible adaptive pedestal level in the integration(s)...
21:59:50 - GENERAL IMAGE LOADER: loading frame /home/hans/astro/data-ssd/M104/Light/Lum/M_104_Light_Lum_300_secs_2020-04-25T00-33-27_013.fits
21:59:50 - 2) CALIBRATE: Adaptive Data Pedestal: enabled
21:59:50 - 2) CALIBRATE: Adaptive Data Pedestal set at: 0 
21:59:50 - 2) CALIBRATE: performing calibration in 32bits normalized floats...
21:59:50 - 2) CALIBRATE: converting data to 32bits normalized floats...
21:59:51 - IMAGE CONVERTER: image conversion not needed, data is already normalized...
21:59:52 - 6) INTEGRATE: got adaptive pedestal level for the integration(s) : 0.0
21:59:52 - 6) INTEGRATE: found: 13 light frames to integrate...
21:59:52 - 6) INTEGRATE: analytical results per frame: 
21:59:52 - 6) INTEGRATE: integration: Luminance - frame: 1 exposure: 300.00 Signal to Noise Ratio (SNR): 8.931E-01 noise 7.846E-03 star density 33 star shape 0.19677 quality 0.76
21:59:52 - 6) INTEGRATE: integration: Luminance - frame: 2 exposure: 300.00 Signal to Noise Ratio (SNR): 8.982E-01 noise 7.847E-03 star density 31 star shape 0.18917 quality 0.70
21:59:52 - 6) INTEGRATE: integration: Luminance - frame: 3 exposure: 300.00 Signal to Noise Ratio (SNR): 9.054E-01 noise 7.813E-03 star density 26 star shape 0.18675 quality 0.56
21:59:52 - 6) INTEGRATE: integration: Luminance - frame: 4 exposure: 300.00 Signal to Noise Ratio (SNR): 9.047E-01 noise 7.828E-03 star density 40 star shape 0.22235 quality 1.05
21:59:52 - 6) INTEGRATE: integration: Luminance - frame: 5 exposure: 300.00 Signal to Noise Ratio (SNR): 9.035E-01 noise 7.840E-03 star density 40 star shape 0.22994 quality 1.07
21:59:52 - 6) INTEGRATE: integration: Luminance - frame: 6 exposure: 300.00 Signal to Noise Ratio (SNR): 9.016E-01 noise 7.839E-03 star density 39 star shape 0.21813 quality 1.03
21:59:52 - 6) INTEGRATE: integration: Luminance - frame: 7 exposure: 300.00 Signal to Noise Ratio (SNR): 9.007E-01 noise 7.835E-03 star density 36 star shape 0.21951 quality 0.93
21:59:52 - 6) INTEGRATE: integration: Luminance - frame: 8 exposure: 300.00 Signal to Noise Ratio (SNR): 8.977E-01 noise 7.832E-03 star density 35 star shape 0.21682 quality 0.90
21:59:52 - 6) INTEGRATE: integration: Luminance - frame: 9 exposure: 300.00 Signal to Noise Ratio (SNR): 8.917E-01 noise 7.834E-03 star density 35 star shape 0.21864 quality 0.91
21:59:52 - 6) INTEGRATE: integration: Luminance - frame: 10 exposure: 300.00 Signal to Noise Ratio (SNR): 8.821E-01 noise 7.860E-03 star density 34 star shape 0.21586 quality 0.88
21:59:52 - 6) INTEGRATE: integration: Luminance - frame: 11 exposure: 300.00 Signal to Noise Ratio (SNR): 8.804E-01 noise 7.868E-03 star density 31 star shape 0.20619 quality 0.76
21:59:52 - 6) INTEGRATE: integration: Luminance - frame: 12 exposure: 300.00 Signal to Noise Ratio (SNR): 8.801E-01 noise 7.885E-03 star density 31 star shape 0.21367 quality 0.76
21:59:52 - 6) INTEGRATE: integration: Luminance - frame: 13 exposure: 300.00 Signal to Noise Ratio (SNR): 8.779E-01 noise 7.883E-03 star density 25 star shape 0.19366 quality 0.57
21:59:52 - 6) INTEGRATE: integration: total exposure time: 3900 seconds = 65.00 minutes = 1.083 hours
21:59:52 - GENERAL IMAGE LOADER: frame /home/hans/astro/data-ssd/M104/Light/Lum/M_104_Light_Lum_300_secs_2020-04-25T00-33-27_013.fits was loaded successfully
21:59:54 - FRAME DETAILS UPDATER: starting...
21:59:54 - FRAME DETAILS UPDATER: no new frames to add
21:59:54 - FRAME DETAILS UPDATER: rebuilding all frame details...
21:59:54 - FRAME DETAILS UPDATER: checking if frames were identified earlier...
21:59:54 - FRAME DETAILS UPDATER: updated succesfully
21:59:54 - CONSTRUCT FRAME DETAILS LIST: starting...
21:59:54 - CONSTRUCT FRAME DETAILS LIST: sorting frames...
21:59:54 - CONSTRUCT FRAME DETAILS LIST: Fixing file arrays...
21:59:54 - CONSTRUCT FRAME DETAILS LIST: numbering frames...
21:59:54 - CONSTRUCT FRAME DETAILS LIST: adding frame marks...
21:59:55 - CONSTRUCT FRAME DETAILS LIST: finished

This APP has stacked other projects with success previously. So it must be related to the data.
APP version: astropixelprocessor-1.078.deb on Ubuntu 18.04.4 LTS

Any things I can try ?