Allow to open multiple projects when some are not imported or without main scene.

(cherry picked from commit b20c20a6f7dbd49dccb7b13123f1914739cd42f6)

editor/project_manager.cpp

@@ -2121,7 +2121,7 @@ void ProjectManager::_run_project_confirm() {
 		if (selected_main == "") {
 			run_error_diag->set_text(TTR("Can't run project: no main scene defined.\nPlease edit the project and set the main scene in the Project Settings under the \"Application\" category."));
 			run_error_diag->popup_centered();
-			return;
+			continue;
 		}
 
 		const String &selected = selected_list[i].project_key;
@@ -2130,7 +2130,7 @@ void ProjectManager::_run_project_confirm() {
 		if (!DirAccess::exists(path + "/.import")) {
 			run_error_diag->set_text(TTR("Can't run project: Assets need to be imported.\nPlease edit the project to trigger the initial import."));
 			run_error_diag->popup_centered();
-			return;
+			continue;
 		}
 
 		print_line("Running project: " + path + " (" + selected + ")");