Fix: Gerrit cannot display Change with non-resolvable Merge Commit

The commit 6fd52badf224e91dd23b6a859d62334672b70803
introduces support for displaying the resolved merge
result in in uploaded merge commits.

However, if the merge commit introduces a merge that
is not resolvable but JGIT (I.e. CrissCross merges),
the automatic merge would fail, throw an unhandled
IOException, effectively not allowing Gerrit to
display the change page at all.

This fix allows gerrit to catch these exception,
allowing the Change to still be reachable through
the WebUI.

Change-Id: I26fbe60695be2c8ec232b50703c5395a0493d4de
1 file changed