PixelPaint: Don't crash when cancel is pressed when saving a file

Previously, we were attempting to add an empty string to the most
recently open files list when no file was saved.

Userland/Applications/PixelPaint/ImageEditor.cpp

@@ -763,6 +763,8 @@ void ImageEditor::save_project()
         return;
     }
     set_unmodified();
+    if (on_file_saved)
+        on_file_saved(path());
 }
 
 void ImageEditor::save_project_as()
@@ -779,6 +781,8 @@ void ImageEditor::save_project_as()
     set_path(file.filename());
     set_loaded_from_image(false);
     set_unmodified();
+    if (on_file_saved)
+        on_file_saved(path());
 }
 
 ErrorOr<void> ImageEditor::save_project_to_file(NonnullOwnPtr<Core::File> file) const

Userland/Applications/PixelPaint/ImageEditor.h

@@ -90,6 +90,8 @@ public:
     Function<void(void)> on_leave;
     Function<void(bool modified)> on_modified_change;
 
+    Function<void(ByteString const& filename)> on_file_saved;
+
     bool request_close();
 
     void save_project_as();

Userland/Applications/PixelPaint/MainWidget.cpp

@@ -208,14 +208,12 @@ ErrorOr<void> MainWidget::initialize_menubar(GUI::Window& window)
         auto* editor = current_image_editor();
         VERIFY(editor);
         editor->save_project_as();
-        GUI::Application::the()->set_most_recently_open_file(editor->path());
     });
 
     m_save_image_action = GUI::CommonActions::make_save_action([&](auto&) {
         auto* editor = current_image_editor();
         VERIFY(editor);
         editor->save_project();
-        GUI::Application::the()->set_most_recently_open_file(editor->path());
     });
 
     file_menu->add_action(*m_new_image_action);
@@ -1441,6 +1439,9 @@ ImageEditor& MainWidget::create_new_editor(NonnullRefPtr<Image> image)
         if (image_editor.active_tool())
             image_editor.active_tool()->on_secondary_color_change(color);
     };
+    image_editor.on_file_saved = [](ByteString const& filename) {
+        GUI::Application::the()->set_most_recently_open_file(filename);
+    };
 
     if (image->layer_count())
         image_editor.set_active_layer(&image->layer(0));