ccf81a6f32
If one switched through guest fast (e.g., keeping the down-arrow key pressed) while staying on the snapshot panel, it could happen that the previous view got already destroyed once the success callback of the feature API request got executed. Then the ExtJS ViewModels' set method got a "null" back from its me.getStub(...) call, and tried to access members of that, resulting in a TypeError exception. Avoid that by checking if we're already destroyed or still around before doing that call. During the time we are already in the callback we shouldn't be able to get destroyed in parallel due to JS single thread nature and no yield point here, so this is safe. Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>