Crash when pressing the '£' key on Belgian Keyboard layout (Cocoa)

In some cases the NSKeyDown event won't have fully constructed string
in the [NSEvent characters]. So we need to add a guard before accessing
the elements of this NSString.

Task-number: QTBUG-12474
Reviewed-by: Richard Moe Gustavsen

1 files changed, 5 insertions, 3 deletions

diff --git a/src/gui/kernel/qt_cocoa_helpers_mac.mm b/src/gui/kernel/qt_cocoa_helpers_mac.mm
index 647cb8671d..7d23abff8a 100644
--- a/src/gui/kernel/qt_cocoa_helpers_mac.mm
+++ b/src/gui/kernel/qt_cocoa_helpers_mac.mm
@@ -685,9 +685,11 @@ bool qt_dispatchKeyEvent(void * /*NSEvent * */ keyEvent, QWidget *widgetToGetEve
     unsigned int info = 0;
     if ([event type] == NSKeyDown) {
         NSString *characters = [event characters];
-        unichar value = [characters characterAtIndex:0];
-        qt_keymapper_private()->updateKeyMap(0, key_event, (void *)&value);
-        info = value;
+        if ([characters length]) {
+            unichar value = [characters characterAtIndex:0];
+            qt_keymapper_private()->updateKeyMap(0, key_event, (void *)&value);
+            info = value;
+        }
     }
 
     // Redirect keys to alien widgets.