Re: [PATCH] gitk: fix error when remote tracking branch is deleted

> When a remote tracking branch is deleted (e.g., via 'git push --delete
> origin branch'), the headids array entry for that branch is removed, but
> upstreamofref may still reference it. This causes gitk to show an error
> and prevents the Tags and Heads view from opening.
> 
> Fix by checking that headids($upstreamofref($n)) exists before accessing
> it in the refill_reflist function.
> 
> Signed-off-by: Michael Rappazzo <rappazzo@gmail.com>

> ---
> To reproduce the case:
> ```
> mkdir sample-repo-remote &&
> cd sample-repo-remote &&
> git init --bare --initial-branch master && 
> cd .. &&
> git clone sample-repo-remote sample-repo &&
> cd sample-repo &&
> git commit --allow-empty -m "Sample commit" &&
> git push origin master &&
> git push origin master:master2 &&
> git branch master2 origin/master2 &&
> git push --delete origin master2
> ```
> Then run gitk --all then bring up the "Tags and Heads" view.
> 
> 
>  gitk | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/gitk b/gitk
> index 6e4d71d585..3cfc9ef291 100755
> --- a/gitk
> +++ b/gitk
> @@ -10294,7 +10294,9 @@ proc refill_reflist {} {
>          if {![string match "remotes/*" $n] && [string match $reflistfilter $n]} {
>              if {[commitinview $headids($n) $curview]} {
>                  lappend localrefs [list $n H]
> -                if {[info exists upstreamofref($n)] && [commitinview $headids($upstreamofref($n)) $curview]} {
> +                if {[info exists upstreamofref($n)] && \
> +                        [info exists headids($upstreamofref($n))] && \
> +                        [commitinview $headids($upstreamofref($n)) $curview]} {
>                      lappend trackedremoterefs [list $upstreamofref($n) R]
>                  }
>              } else {