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

See also f5a37ae.

CHANGELOG.md

@@ -42,6 +42,7 @@ Other new features:
 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

@@ -1024,7 +1024,7 @@ 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);
 
         hoveredRow = r;