Protect case when opening an empty file in update mode. fix https://savannah.cern.ch/bugs/?69423
Protect case when opening an empty file in update mode.
fix https://savannah.cern.ch/bugs/?69423


git-svn-id: ecbadac9c76e8cf640a0bca86f6bd796c98521e3@34281 27541ba8-7e3a-0410-8455-c3a389f83636

bbannier/ROOT,bbannier/ROOT,bbannier/ROOT,dawehner/root,dawehner/root,dawehner/root,dawehner/root,bbannier/ROOT,dawehner/root,dawehner/root,dawehner/root,dawehner/root,bbannier/ROOT,bbannier/ROOT,bbannier/ROOT