Bug 6280 : Don't generate invalid SQL in GetPendingIssues

Bug 6280 : Don't generate invalid SQL in GetPendingIssues

Change to parameter list in GetPendingIssues made it
callable by an empty list resulting in invalid sql being
sent to server. As this was occuring on most issues error log
was filling up. Put safeguard in the routine
Also don't bother calling when you have no need

Some of the processing was needlessly obscure

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Paul Poulain <paul.poulain@biblibre.com>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>