handle errors in main entry point

src/app/core/controller.cc

@@ -244,11 +244,12 @@ void Controller::OnInput() {
   HandleMouseMovement(wheel);
 }
 
-void Controller::OnLoad() {
+absl::Status Controller::OnLoad() {
   if (master_editor_.quit()) {
     active_ = false;
   }
-  PRINT_IF_ERROR(master_editor_.Update());
+  RETURN_IF_ERROR(master_editor_.Update());
+  return absl::OkStatus();
 }
 
 void Controller::DoRender() const {

src/app/core/controller.h

@@ -33,7 +33,7 @@ class Controller : public ExperimentFlags {
   bool IsActive() const { return active_; }
   absl::Status OnEntry(std::string filename = "");
   void OnInput();
-  void OnLoad();
+  absl::Status OnLoad();
   void DoRender() const;
   void OnExit();