OS X: fix another out-of-bounds TW.META access.

See also e1d6dac.

CHANGELOG.md

@@ -7,6 +7,7 @@ Changelog
 Bug fixes:
   * Do not crash when applying a symmetry constraint to two points.
   * Fix TTF font metrics again (properly this time).
+  * Various minor crashes.
 
 2.2
 ---

src/textwin.cpp

@@ -988,7 +988,7 @@ void TextWindow::MouseEvent(bool leftClick, bool leftDown, double x, double y) {
             break;
         }
     }
-    if(r >= rows || c >= MAX_COLS) {
+    if(r < 0 || c < 0 || r >= rows || c >= MAX_COLS) {
         SetMousePointerToHand(false);
         goto done;
     }