Prevent subsequent panics for already borrowed editor (#689)

Fix double panic

frontend/wasm/src/editor_api.rs

@@ -65,17 +65,22 @@ impl JsEditorHandle {
 		}
 
 		let frontend_messages = EDITOR_INSTANCES.with(|instances| {
-			instances
-				.borrow_mut()
+			instances.try_borrow_mut().map(|mut editors| {
+				editors
 					.get_mut(&self.editor_id)
 					.expect("EDITOR_INSTANCES does not contain the current editor_id")
 					.handle_message(message.into())
+			})
 		});
+
+		if let Ok(frontend_messages) = frontend_messages {
 			for message in frontend_messages.into_iter() {
 				// Send each FrontendMessage to the JavaScript frontend
 				self.send_frontend_message_to_js(message);
 			}
 		}
+		// If the editor cannot be borrowed then it has encountered a panic - we should just ignore new dispatches
+	}
 
 	// Sends a FrontendMessage to JavaScript
 	fn send_frontend_message_to_js(&self, message: FrontendMessage) {