A single corrupt change, e.g. with a missing current patch set, can
potentially prevent a search results page from loading by causing the
whole query to return a 500.
Instead of hosing search results, omit corrupt changes from the
results with a warning in the logs.
The downside of this approach is that in the presence of corrupt
changes, it is no longer guaranteed that _more_changes will be set on
the last result only if there were N results. On balance I think this
is a fair price to keep the web UI usable for users in this rare error
case.
Change-Id: I1a2a24877156c55243513b03207137d412bc8bfd
b7fd8de1cf