Wait for result before removing observers in BatchAlgorithmRunner destructor

[SilkeSchomann]

Description of work

This PR fixes a crash when closing the AlfView interface at the same time as the interface is still loading data.

Closing the AlfView interface results in a call to the destructor of the BatchAlgorithmRunner. If this happens while the interface is still loading data, the notification that data loading is complete causes an exception. A brief wait for the result in the destructor prevents this.

Fixes #38136.

To test:

Follow the instructions on the original issue.

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[adriazalvarez]

I don't get a crash following instructions on ALFVIew.
Thanks for fixing this.