patch 8.2.3756: might crash when callback is not valid Commit: https://github.com/vim/vim/commit/4dc24eb5adbcc76838fae1e900936dd230209d96 Author: Yegappan Lakshmanan <yegappan@yahoo.com> Date: Tue Dec 7 12:23:57 2021 +0000 patch 8.2.3756: might crash when callback is not valid Problem: might crash when callback is not valid. Solution: Check for valid callback. (Yegappan Lakshmanan, closes https://github.com/vim/vim/issues/9293)

|x+0&#ffffff0@4> |1+0&#ffff4012|2|3| +0&#ffffff0|x| @63
|x@4|1+0&#ffff4012|2|3| +0&#ffffff0|x| @64
|x@4|2+0&#ffff4012|3| +0&#ffffff0|x| @65
|x@4|3+0&#ffff4012| +0&#ffffff0|x| @66
|x@4| |x| @67
|x@3| |x@1| @67
|x@2| |1+0&#ffff4012|x+0&#ffffff0@1| @67
|x@1| |1+0&#ffff4012|2|x+0&#ffffff0@1| @67
|x| |1+0&#ffff4012|2|3|x+0&#ffffff0@1| @67
@1|1+0&#ffff4012|2|3| +0&#ffffff0|x@1| @67
|~+0#4040ff13&| @73
| +0#0000000&@56|1|,|6| @10|A|l@1|