Fix 0011364: htmlentities invalid parameter type on pretend install

When pretending to install/upgrade MantisBT by writing SQL queries to
output rather than executing them, the following error would be
encountered:

SYSTEM WARNING: htmlentities() expects parameter 1 to be string, array
given

Now we don't attempt to log upgrade function calls in amongst the dumped
query strings.

Thanks to Otto Giesenfeld for this patch (modified).