LibGUI: Tolerate Window::set_icon(nullptr)

Don't try to dereference a null icon. Instead just set a 16x16 empty
bitmap as the window icon.

This looks like the crash mentioned in #3817.

1 files changed, 4 insertions, 2 deletions

diff --git a/Libraries/LibGUI/Window.cpp b/Libraries/LibGUI/Window.cpp
index 1618e891c3..e71a939d69 100644
--- a/Libraries/LibGUI/Window.cpp
+++ b/Libraries/LibGUI/Window.cpp
@@ -682,9 +682,11 @@ void Window::set_icon(const Gfx::Bitmap* icon)
     if (m_icon == icon)
         return;
 
-    m_icon = create_shared_bitmap(Gfx::BitmapFormat::RGBA32, icon->size());
+    Gfx::IntSize icon_size = icon ? icon->size() : Gfx::IntSize(16, 16);
+
+    m_icon = create_shared_bitmap(Gfx::BitmapFormat::RGBA32, icon_size);
     ASSERT(m_icon);
-    {
+    if (icon) {
         Painter painter(*m_icon);
         painter.blit({ 0, 0 }, *icon, icon->rect());
     }