Merge branch 'dl/push-missing-object-error' into maint-2.51

"git push" had a code path that led to BUG() but it should have been a die(), as it is a response to a usual but invalid end-user action to attempt pushing an object that does not exist. cf. <xmqqo6spiyqp.fsf@gitster.g> * dl/push-missing-object-error: remote.c: convert if-else ladder to switch remote.c: remove BUG in show_push_unqualified_ref_name_error() t5516: remove surrounding empty lines in test bodies