Crash while changing the windows flags from a Qt::Drawer window on Cocoa

The crash was caused while checking the visibility of the toolbar inside
a native cocoa window. There is no toolbar for a drawer window.

Task-number: QTBUG-11138
Reviewed-by: Denis

1 files changed, 5 insertions, 3 deletions

diff --git a/src/gui/kernel/qwidget_mac.mm b/src/gui/kernel/qwidget_mac.mm
index a9bb691..e57ec77 100644
--- a/src/gui/kernel/qwidget_mac.mm
+++ b/src/gui/kernel/qwidget_mac.mm
@@ -2861,9 +2861,11 @@ void QWidgetPrivate::setParent_sys(QWidget *parent, Qt::WindowFlags f)
         }
         if (wasWindow) {
             oldToolbar = [oldWindow toolbar];
-            [oldToolbar retain];
-            oldToolbarVisible = [oldToolbar isVisible];
-            [oldWindow setToolbar:nil];
+            if (oldToolbar) {
+                [oldToolbar retain];
+                oldToolbarVisible = [oldToolbar isVisible];
+                [oldWindow setToolbar:nil];
+            }
         }
 #endif
     }