fix a bug in using option "d" in  projection, when there is not an existing pad (gPad=0)
This fixes the issue reported in http://root.cern.ch/phpBB3/viewtopic.php?f=3&t=16308 by S. Schmitt


git-svn-id: https://root.cern.ch/svn/root/trunk@49317 27541ba8-7e3a-0410-8455-c3a389f83636