Progress calculation of export job is wrong if objects contain multiple images

[moi90]

In this project, each object has two images:
https://ecotaxa.obs-vlfr.fr/prj/6433

When exporting, the job progress counts the number of written rows and the total number of objects:

127 % | Row 1050000 of max 785405

Instead of counting rows, it should rather count the number of processed objects so that the percentages are correctly calculated.

[grololo06]

Nice one!