CatalogueUI : Fix incorrect sorting of images
CatalogueUI : Fix incorrect sorting of images

#3684 highlighted a case where the `ImagesPath` could end up being
pre-sorted before we call `setSortable( False ). Disabling sorting in
the constructor fixes this.

Fixes #3684.

GafferHQ/gaffer,andrewkaufman/gaffer,andrewkaufman/gaffer,boberfly/gaffer,johnhaddon/gaffer,GafferHQ/gaffer,lucienfostier/gaffer,ImageEngine/gaffer,johnhaddon/gaffer,hradec/gaffer,hradec/gaffer,johnhaddon/gaffer,GafferHQ/gaffer,andrewkaufman/gaffer,boberfly/gaffer,boberfly/gaffer,johnhaddon/gaffer,boberfly/gaffer,ImageEngine/gaffer,lucienfostier/gaffer,andrewkaufman/gaffer,hradec/gaffer,GafferHQ/gaffer,lucienfostier/gaffer,hradec/gaffer,GafferHQ/gaffer,ImageEngine/gaffer,hradec/gaffer,johnhaddon/gaffer,ImageEngine/gaffer,andrewkaufman/gaffer,lucienfostier/gaffer