Moved the test for the vistal type so that the list of preferred extensions is used except if vistal images are present.
Moved the test for the vistal type so that the list of preferred extensions is used except if vistal images are present.

rdebroiz/medInria-public,NicolasSchnitzler/medInria-public,aabadie/medInria-public,rdebroiz/medInria-public,rdebroiz/medInria-public,NicolasSchnitzler/medInria-public,aabadie/medInria-public,aabadie/medInria-public,NicolasSchnitzler/medInria-public