Release pipeline: Use of announcement gist results in TAG_URL variable not being set

[mthalman]

The release pipeline allows you the option of referencing a gist URL that will be used as the content for the release announcement instead of automatically generating it. When that parameter is provided, it results in the following error when executing the Submit announcement discussion task in the release stage:

line 62: TAG_URL: unbound variable

This is because that variable only gets set as a result of running the create-announcement-draft.sh script. But that script doesn't get run when an announcement gist URL is provided.

The same applies for the use of the RELEASE_NOTES_URL variable.

[dotnet-issue-labeler]

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[ali-turan7]

TAG_URL and RELEASE_NOTES_URL variables are removed from being printed in release.yml