Fix repeated key and beat analysis with default settings

[uklotzde]

Found while analyzing #2773.

Ideally the settings should never return an empty value, but I won't fix this.

[Be-ing]

Thank you, this fixes the bug with some of my tracks mysteriously not having beats detected.

[uklotzde]

I noticed even more issues about how the beat analyzer decides when to execute the analysis and when finished how to store the results. But I'll stop at this point and leave the rewrite to someone else. It is to dangerous to touch this code without the ability to test all code paths.

[Be-ing]

Uhhh yeah something is very wrong here... now when I do batch analysis, many files still don't have a BPM marked, and those that do all show the same value for BPM... 😕

[uklotzde]

@be Did you try to reset the BPM of those tracks before analyzing them?

Tracks with an invalid BPM (<= 0) might not be re-analyzed depending on the settings and the database contents. This doesn't make sense to me. Those tracks should always be re-analyzed.

[uklotzde]

Track that have been reset while the database column was missing need to be reset again.

[Be-ing]

Yes, I reset the BPM and beatgrid from the track context menu. I am experimenting with a fresh database now...

[uklotzde]

Testing with a fresh database revealed no new issues.

[Be-ing]

Now zero tracks have a BPM detected with a fresh database... 😕

[Be-ing]

Nevermind, I was testing with this branch only. With the 2.3 branch including #2773, BPMs are showing up when analyzing with a fresh databse.

[uklotzde]

Those issues occur when resetting the bpm with the database column update missing. We could mitigate the issues for early testers by re-analyzing always if bpm <= 0.

[uklotzde]

The commit in #2776 could fix some inconsistent database entries.