Manually stopping/aborting acquisition fails

[tudorp]

In latest next branch snapshot, when using a Sump based device, trying to abort a capture before, or after the hardware acquisition is triggered, fails by rendering the GUI unusable for launching a new capture, for most of the times.

Diagnosis: After several failures (that require restarting the application completely) I managed to successfully stop once the acquisition after being triggered and before finishing. Exactly after that I managed to successfully stop an acquisition not triggered yet. The third attempt faced the above mentioned issues.It seems that the Task execution complete is being fired but not also the Acquisition complete event, but I couldn't manage to find the root cause.

PS: For testing purposes I tried removing the exception thrown when no samples are collected (stop before acq. is triggered), but that didn't help solve the issue or pin down a more precise root cause.