Caused by rBfffba2b6530.
In above commit, the buttons rnaindex [-1 for entire arrays like colors]
was not used anymore for the entire function body of
`ED_autokeyframe_property` (previously in `ui_but_anim_autokey`).
Replacing the index with 0 (in the array case) is indeed necessary for
`BKE_fcurve_find_by_rna_context_ui`, prior to rBfffba2b6530 this was
taken care of by using `ui_but_get_fcurve` instead [which did this
internally].
But using an index of 0 (instead of -1) for the entire function body of
`ED_autokeyframe_property` fails for the array part later, namely
`insert_keyframe` needs -1 here.
Now just replace the index for //finding the FCurve//, but use the
original for //inserting the keyframe//.
Could be backported to 2.83 LTS.
Reviewers: campbellbarton, sybren
Subscribers:
08286ef8ba