Fix build bustage due to 'error: comparison of unsigned expression >= 0 is always true [-Werror=type-limits]' after bug 1018288 landing in m-c. Part 2. rs=bustage-fix CLOSED TREE

db/mork/src/morkNode.cpp

@@ -380,8 +380,8 @@ nsIMdbFile_SlotStrongFile(nsIMdbFile* self, morkEnv* ev, nsIMdbFile** ioSlot)
       *ioSlot = 0;
       NS_RELEASE(file);
     }
-    if ( self && ev->Good() && (NS_ADDREF(self)>=0) && ev->Good() )
-      *ioSlot = self;
+    if (self && ev->Good())
+      NS_ADDREF(*ioSlot = self);
   }
 }