Add if exists guard to DROP DATABASE command

This script can sometimes be called when the database is not yet created, currently it spits out errors

Author: Ammarpad

deletewiki.sh

@@ -4,4 +4,4 @@ set -ex
 rm -rf $PATCHDEMO/wikis/$WIKI
 
 # delete database
-mysql -u patchdemo --password=patchdemo -e "DROP DATABASE patchdemo_$WIKI";
+mysql -u patchdemo --password=patchdemo -e "DROP DATABASE IF EXISTS patchdemo_$WIKI";