Adding a sanity pointer check to prevent crash; Use png instead of jpg for thumbnails to preserve transparent background; Adding default extension for fibers (xml)
Adding a sanity pointer check to prevent crash; Use png instead of jpg for thumbnails to preserve transparent background; Adding default extension for fibers (xml)

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