BUG: GetDefiniton can return null

Source/cmElseCommand.cxx

@@ -118,7 +118,7 @@ bool cmElseCommand::InitialPass(std::vector<std::string> const& args)
     cmRegularExpression regEntry(args[2].c_str());
     
     // check for black line or comment
-    if (regEntry.find(def))
+    if (def && regEntry.find(def))
       {
       f = new cmIfFunctionBlocker();
       }