sync: uninitialized variable on mirror sync failure
sync: uninitialized variable on mirror sync failure

When repo sync fails, if the workspace is a mirror, an uninitialized
variable is referenced.

Bug: crbug.com/gerrit/16356
Change-Id: I1dba9f92319b9cbfd18460327560a395c88a089f
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/349654
Reviewed-by: Sam Saccone <1dc92ef42dd4a9b5cf1cf135ebbd3434b0189447@google.com>
Reviewed-by: Xin Li <93465216fd46a440eb04b27d6e009aced8b0c153@google.com>
Tested-by: LaMont Jones <01939f9990a33aa2509cfaed21d2f9ba201a2b37@google.com>

lewixliu/git-repo,GerritCodeReview/git-repo,GerritCodeReview/git-repo,lewixliu/git-repo