Issue #722: check camera3d presence in rotateCamera()

src/extensions/tmdet/camera.ts

@@ -43,6 +43,10 @@ export async function rotateCamera(plugin: PluginUIContext) {
         return Vec3.add(Vec3(), v, u);
     }
 
+    if (!plugin.canvas3d) {
+        return;
+    }
+
     const cam = plugin.canvas3d!.camera;
     const snapshot = cam.getSnapshot();
     const newSnapshot = {