Fix extNb for FITS image HDU

[jmmc-opendev]

Fix extNb for FITS image HDU

[bourgesl]

Impact study then propose a solution

[Hitogoroshi]

Usages of FitsHDU.setExtNb [4 occurrences]

FitsImageLoader.java
createImageHDU
  522:  imageHDU.setExtNb(hduIndex);

OIFitsFile.java
addOiTable
  164:  oiTable.setExtNb(getNbOiTables());
This setter take the number of OITable as counter.
The other take the index of HDU (index in the file when it is loading)

OIFitsLoader.java
processHDUnits
  435:  oiTable.setExtNb(hduIndex);
  487:  oiTable.setExtNb(hduIndex);

So the problem comes from the difference in the uses of the setter.

[bourgesl]

Thanks for the usages.
What do you propose to test the bug & fix it ?

[Hitogoroshi]

During the analysis I do not have any problems when reading a file or its writing.
It would be necessary to review how indexes are managed during the creation of a memory structure.