Mixxx 2.1.6

Changelog:

• Fix crash when loading a Qt5 Soundsource / Vamp Plug-In. lp:1774639 * Validate effect parameter range. lp:1795234
• Fix crash using the bpm_tap button without a track loaded. lp:1801844
• Fix possible crash after ejecting a track. lp:1801874
• Fix wrong bitrate reported for faulty mp3 files. lp:1782912
• Fix Echo effect syncing lp:1793232
• Fix iTunes context menu lp:1799932
• Fix loading the wrong track after delete search and scroll. lp:1803148
• Improve search bar timing. lp:1635087
• Fix quoted search sentence. lp:1784141
• Fix loading a track formerly not existing. lp:1800395
• Fix imporing m3u files with blank lines. lp:1806271
• Fix position in sampler overview waveforms. lp:1744170
• Don't reset rate slider, syncing a track without a beatgrid. lp:1783020
• Clean up iTunes track context menu. lp:1800335
• Collapsed sampler are not analyzed on startup. lp:1801126
• search for decoration characters like "˚". lp:#1802730
• Fix cue button blinking after pressing eject on an empty deck. lp:1808222