You could trigger invalid states by pressing the recording button
while the profiler was waiting for data to be loaded from the
application or by pressing the "stop" button twice. Now the buttons
are disabled when they don't make any sense. In particular you cannot
clear, change features, filter the display while recording and you
cannot toggle the recording while loading. Pressing the "stop" button
twice will cancel the loading now, similar to what happens if you
first disable recording and then stop while the data is loaded.

Change-Id: Ie5133f4bed76593dedc9763b778a2c5c17187543
Reviewed-by: Tobias Hunger <tobias.hunger@theqtcompany.com>