In the bugdoc of tdf#91807 there are at least 49 corrupt zip streams
that raise exceptions in the DeflateThreads.  Because the maximum
allowed number of threads happens to be 48, this results in an infinite
loop in ZipOutputStream::reduceScheduledThreadsToGivenNumberOrLess().

(regression from 7e2ea27e)

In case an exception is thrown, don't re-throw it immediately, which
might cause trouble such as leaking all of the ZipOutputEntry instances
in m_aEntries.

Change-Id: Ia74ab8e46fa1349c049d05dbec3454bfbe7d61d9