Fix crash happening when deleting a remote branch. Closes #2538.
GetFullBranchName() test added
ChangeLog updated
Merge remote-tracking branch 'refs/remotes/origin/release/2.48' into release/2.48

Conflicts:
	GitExtensionsTest/GitCommands/Git/GitCommandHelpersTest.cs
	GitExtensionsTest/GitExtensionsTest.csproj