fix: guard against uninitialized codemirror instance (#246)

In obsidian (>=v1.7.2?) the codemirror instance is often not unitialized
at times, triggering some uncaught exceptions. This is particularly
noticable when:

- (w/ "Vim chord display" enabled) opening the vault w/o a note opened
- closing all tabs and opening a note

Add some null guards to avoid these errors

Author: baodrate

main.ts

@@ -153,6 +153,7 @@ export default class VimrcPlugin extends Plugin {
 		if (!view) return;
 
 		let cm = this.getCodeMirror(view);
+		if (!cm) return;
 		if (
 			this.getCursorActivityHandlers(cm).some(
 				(e: { name: string }) => e.name === "updateSelection")
@@ -180,6 +181,8 @@ export default class VimrcPlugin extends Plugin {
 			this.currentVimStatus = vimStatus.normal;
 			if (this.settings.displayVimMode)
 				this.updateVimStatusBar();
+
+			if (!cmEditor) return;
 			cmEditor.off('vim-mode-change', this.logVimModeChange);
 			cmEditor.on('vim-mode-change', this.logVimModeChange);
 
@@ -580,7 +583,9 @@ export default class VimrcPlugin extends Plugin {
 			this.vimChordStatusBar.parentElement.insertBefore(this.vimChordStatusBar, parent.firstChild);
 			this.vimChordStatusBar.style.marginRight = "auto";
 
-			let cmEditor = this.getCodeMirror(this.getActiveView());
+			const view = this.getActiveView();
+			if (!view) return;
+			let cmEditor = this.getCodeMirror(view);
 			// See https://codemirror.net/doc/manual.html#vimapi_events for events.
 			cmEditor.off('vim-keypress', this.onVimKeypress);
 			cmEditor.on('vim-keypress', this.onVimKeypress);