XML Datamodel: new format (fixed issue seen with some versions of PHP)

git-svn-id: http://svn.code.sf.net/p/itop/code/trunk@2346 a333f486-631f-4898-b8df-5754b55c2be0

setup/modelfactory.class.inc.php

@@ -1409,7 +1409,7 @@ class MFElement extends DOMElement
 				}
 				else
 				{
-					$aRanks[] = max($aRanks) + 1;
+					$aRanks[] = count($aRanks) > 0 ? max($aRanks) + 1 : 0;
 				}
 				array_multisort($aRanks, $res);
 			}