Clear canvas item after rendering font, fixes #23774

editor/plugins/editor_preview_plugins.cpp

@@ -845,15 +845,16 @@ Ref<Texture> EditorFontPreviewPlugin::generate_from_path(const String &p_path, c
 
 	font->draw(canvas_item, pos, sampled_text);
 
-	VS::get_singleton()->viewport_set_update_mode(viewport, VS::VIEWPORT_UPDATE_ONCE); //once used for capture
-
 	preview_done = false;
+	VS::get_singleton()->viewport_set_update_mode(viewport, VS::VIEWPORT_UPDATE_ONCE); //once used for capture
 	VS::get_singleton()->request_frame_drawn_callback(const_cast<EditorFontPreviewPlugin *>(this), "_preview_done", Variant());
 
 	while (!preview_done) {
 		OS::get_singleton()->delay_usec(10);
 	}
 
+	VS::get_singleton()->canvas_item_clear(canvas_item);
+
 	Ref<Image> img = VS::get_singleton()->texture_get_data(viewport_texture);
 	ERR_FAIL_COND_V(img.is_null(), Ref<ImageTexture>());
 
@@ -878,7 +879,11 @@ Ref<Texture> EditorFontPreviewPlugin::generate_from_path(const String &p_path, c
 
 Ref<Texture> EditorFontPreviewPlugin::generate(const RES &p_from, const Size2 p_size) const {
 
-	return generate_from_path(p_from->get_path(), p_size);
+	String path = p_from->get_path();
+	if (!FileAccess::exists(path)) {
+		return Ref<Texture>();
+	}
+	return generate_from_path(path, p_size);
 }
 
 EditorFontPreviewPlugin::EditorFontPreviewPlugin() {