Fix possible crash on invalid active track

Fixes #114
2 jobs for Applications/19.04 in 14 minutes and 49 seconds (queued for 1 second)
Status Name Job ID Coverage
  Build
passed freebsd stable-kf5-qt5 qt5.12 #2768
freebsd

00:07:17

passed linux stable-kf5-qt5 qt5.10 #2767

00:14:48

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