Handle onWillFire if it fails, so it loads dom renderer

addons/xterm-addon-webgl/src/WebglRenderer.ts

@@ -103,9 +103,6 @@ export class WebglRenderer extends Disposable implements IRenderer {
       throw new Error('WebGL2 not supported ' + this._gl);
     }
 
-    // TODO: Remove me.
-    throw new Error('WebGL2 not supported ' + this._gl);
-
     this.register(addDisposableDomListener(this._canvas, 'webglcontextlost', (e) => {
       console.log('webglcontextlost event received');
       // Prevent the default behavior in order to enable WebGL context restoration.

src/browser/Terminal.ts

@@ -515,7 +515,10 @@ export class Terminal extends CoreTerminal implements ITerminal {
     // Performance: Add viewport and helper elements from the fragment
     this.element.appendChild(fragment);
 
-    this._onWillOpen.fire(this.element);
+    try {
+      this._onWillOpen.fire(this.element);
+    }
+    catch { /* fails to load addon for some reason */ }
     if (!this._renderService.hasRenderer()) {
       this._renderService.setRenderer(this._createRenderer());
     }