Expression index can get an empty generated column name

Applying: Avoid empty generated names for expression index columns
Using index info to reconstruct a base tree...
M	src/backend/commands/indexcmds.c
M	src/test/regress/expected/create_index.out
M	src/test/regress/sql/create_index.sql
Falling back to patching base and 3-way merge...
Auto-merging src/test/regress/sql/create_index.sql
Auto-merging src/test/regress/expected/create_index.out
Auto-merging src/backend/commands/indexcmds.c
CONFLICT (content): Merge conflict in src/backend/commands/indexcmds.c
Patch failed at 0001 Avoid empty generated names for expression index columns

error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
hint: When you have resolved this problem, run "git am --continue".
hint: If you prefer to skip this patch, run "git am --skip" instead.
hint: To restore the original branch and stop patching, run "git am --abort".
hint: Disable this message with "git config advice.mergeConflict false"