Don't crash wk when ad-hoc meshing fails (#8716)

Previously, wk crashed completely when the ad-hoc meshing fails (e.g.,
because the backend timed out). There are also other sagas which could
be made more resilient, but that's something bigger in my opinion (see
#8715).
Therefore, this PR simply adds a simple try-catch and an error toast.

### URL of deployed dev instance (used for testing):
- https://___.webknossos.xyz

### Steps to test:
- I added a `throw new Error("...")` to the meshing saga and got a
simple error toast asking me to retry
- no need to test further in my opinion

### Issues:
- contributes to #8715

------
(Please delete unneeded items, merge only when none are left open)
- [x] Added changelog entry (create a `$PR_NUMBER.md` file in
`unreleased_changes` or use `./tools/create-changelog-entry.py`)

Author: philippotto

frontend/javascripts/viewer/model/sagas/meshes/ad_hoc_mesh_saga.ts

@@ -6,6 +6,7 @@ import {
 import ThreeDMap from "libs/ThreeDMap";
 import ErrorHandling from "libs/error_handling";
 import { V3 } from "libs/mjs";
+import Toast from "libs/toast";
 import { sleep } from "libs/utils";
 import _ from "lodash";
 import type { ActionPattern } from "redux-saga/effects";
@@ -177,15 +178,20 @@ function* loadAdHocMeshFromAction(action: LoadAdHocMeshAction): Saga<void> {
   // Remove older mesh instance if it exists already.
   yield* put(removeMeshAction(layer.name, action.segmentId));
 
-  yield* call(
-    loadAdHocMesh,
-    action.seedPosition,
-    action.seedAdditionalCoordinates,
-    action.segmentId,
-    false,
-    layer.name,
-    action.extraInfo,
-  );
+  try {
+    yield* call(
+      loadAdHocMesh,
+      action.seedPosition,
+      action.seedAdditionalCoordinates,
+      action.segmentId,
+      false,
+      layer.name,
+      action.extraInfo,
+    );
+  } catch (exc) {
+    Toast.error(`The mesh for segment ${action.segmentId} could not be loaded. Please try again.`);
+    ErrorHandling.notify(exc as any);
+  }
 }
 
 export function* getMeshExtraInfo(

unreleased_changes/8716.md

@@ -0,0 +1,2 @@
+### Fixed
+- Fixed a crash when an ad-hoc mesh could not be loaded for some reason.