Fix crash if an exception happens in DelayedMouseMove::commitMouseMove()

Without this an exception in DelayedMouseMove::commitMouseMove() could
produce (e.g.) the crash in #3818. This same error handling was
already done for Editor::onProcessMessage() in
DocView::onProcessMessage() to avoid crashing due unhandled exceptions
in Editor message processing.

src/app/ui/doc_view.cpp

@@ -167,15 +167,7 @@ protected:
       return Editor::onProcessMessage(msg);
     }
     catch (const std::exception& ex) {
-      EditorState* state = getState().get();
-
-      Console console;
-      Console::showException(ex);
-      console.printf("\nInternal details:\n"
-        "- Message type: %d\n"
-        "- Editor state: %s\n",
-        msg->type(),
-        state ? typeid(*state).name(): "None");
+      showUnhandledException(ex, msg);
       return false;
     }
   }

src/app/ui/editor/delayed_mouse_move.cpp

@@ -71,7 +71,12 @@ void DelayedMouseMove::commitMouseMove()
   if (m_timer.isRunning())
     m_timer.stop();
 
-  m_delegate->onCommitMouseMove(m_editor, spritePos());
+  try {
+    m_delegate->onCommitMouseMove(m_editor, spritePos());
+  }
+  catch (const std::exception& ex) {
+    m_editor->showUnhandledException(ex, nullptr);
+  }
 }
 
 const gfx::PointF& DelayedMouseMove::spritePos() const

src/app/ui/editor/editor.cpp

@@ -1897,6 +1897,21 @@ void Editor::cancelSelections()
   clearSlicesSelection();
 }
 
+void Editor::showUnhandledException(const std::exception& ex,
+                                    const ui::Message* msg)
+{
+  EditorState* state = getState().get();
+
+  Console console;
+  Console::showException(ex);
+  console.printf(
+    "\nInternal details:\n"
+    "- Message type: %d\n"
+    "- Editor state: %s\n",
+    (msg ? msg->type(): -1),
+    (state ? typeid(*state).name(): "None"));
+}
+
 //////////////////////////////////////////////////////////////////////
 // Message handler for the editor
 

src/app/ui/editor/editor.h

@@ -322,6 +322,11 @@ namespace app {
     // Properties to show information in the status bar
     bool showAutoCelGuides() const { return m_showAutoCelGuides; }
 
+    // Used in case an unhandled exception was caught when processing
+    // an Editor or EditorState event.
+    void showUnhandledException(const std::exception& ex,
+                                const ui::Message* msg);
+
     static void registerCommands();
 
   protected: