Please see https://bugzilla.redhat.com/show_bug.cgi?id=1048499 and https://retrace.fedoraproject.org/faf/reports/214888/
It looks like in certain circumstances restoring the latest selection on starup on a item with enclosures happens before the enclosure view is created.
I personally can't reproduce atm.
I can reproduce it when Liferea starts up from warm cache in <10% of the cases. It is a race condition when the item is loaded faster then the widgets are there :-(
Quick fixed with an ugly workaround. When it happens now the item list view will look uninitialized (which auto-fixes by clicking any feed). I think this is better than the crash.
Will be released with 1.10.6 and 1.11. I plan a rewrite to address it properly for 1.11 line.
Fixed in git for now