SpriteFramesEditor Fix crash when selecting non-Texture2D file for splitting

editor/plugins/sprite_frames_editor_plugin.cpp

@@ -285,7 +285,7 @@ void SpriteFramesEditor::_sheet_spin_changed(double) {
 }
 
 void SpriteFramesEditor::_prepare_sprite_sheet(const String &p_file) {
-	Ref<Resource> texture = ResourceLoader::load(p_file);
+	Ref<Texture2D> texture = ResourceLoader::load(p_file);
 	if (!texture.is_valid()) {
 		EditorNode::get_singleton()->show_warning(TTR("Unable to load images"));
 		ERR_FAIL_COND(!texture.is_valid());