[FIX] mail, web: correctly handle mounting operation cancelled error

addons/mail/static/src/messaging/widget/form_renderer/form_renderer.js

@@ -111,7 +111,13 @@ FormRenderer.include({
      * @private
      */
     async _mountChatterContainerComponent() {
-        await this._chatterContainerComponent.mount(this._chatterContainerTarget);
+        try {
+            await this._chatterContainerComponent.mount(this._chatterContainerTarget);
+        } catch (error) {
+            if (error.message !== "Mounting operation cancelled") {
+                throw error;
+            }
+        }
     },
     /**
      * @override
@@ -141,17 +147,23 @@ FormRenderer.include({
             if (!this._chatterContainerComponent) {
                 this._makeChatterContainerComponent();
             } else {
-                this._updateChatterContainerComponent();
+                await this._updateChatterContainerComponent();
             }
             await this._mountChatterContainerComponent();
         }
     },
     /**
      * @private
      */
-    _updateChatterContainerComponent() {
+    async _updateChatterContainerComponent() {
         const props = this._makeChatterContainerProps();
-        this._chatterContainerComponent.update(props);
+        try {
+            await this._chatterContainerComponent.update(props);
+        } catch (error) {
+            if (error.message !== "Mounting operation cancelled") {
+                throw error;
+            }
+        }
     },
 
     //--------------------------------------------------------------------------

addons/web/static/lib/owl/owl.js

@@ -3174,8 +3174,7 @@
             if (index >= 0) {
                 const [task] = this.tasks.splice(index, 1);
                 fiber.cancel();
-                // Do not leak Mounting operation cancelled as a crash: https://github.com/odoo/owl/issues/676
-                fiber.error = reason;
+                fiber.error = new Error(reason);
                 task.callback();
             }
         }