Rename Note: Ensure markdown files end with .md

This broke when supporting txt files

lib/core/note.dart

@@ -306,24 +306,26 @@ class Note with NotesNotifier {
   void rename(String newName) {
     // Do not let the user rename it to a non-markdown file
     switch (_fileFormat) {
-      case NoteFileFormat.Markdown:
-        if (!newName.toLowerCase().endsWith('.md')) {
-          newName += '.md';
-        }
-        break;
-
       case NoteFileFormat.Txt:
         if (!newName.toLowerCase().endsWith('.txt')) {
           newName += '.txt';
         }
         break;
+
+      case NoteFileFormat.Markdown:
+      default:
+        if (!newName.toLowerCase().endsWith('.md')) {
+          newName += '.md';
+        }
+        break;
     }
 
     var oldFilePath = filePath;
     var parentDirName = p.dirname(filePath);
     var newFilePath = p.join(parentDirName, newName);
-    if (_loadState != NoteLoadState.None) {
-      // for new notes
+
+    // The file will not exist for new notes
+    if (File(oldFilePath).existsSync()) {
       File(filePath).renameSync(newFilePath);
     }
     _filePath = newFilePath;

lib/screens/note_editor.dart

@@ -229,6 +229,7 @@ class NoteEditorState extends State<NoteEditor> {
           note = _note;
           note.rename(fileName);
         });
+        return;
       }
       var container = Provider.of<StateContainer>(context, listen: false);
       container.renameNote(note, fileName);