[Trunk] Determine tempo from text doesn't reflect playback BPM correctly

Hi people,

I'm actually testing the build 4313 of musescore 2.
Reproduce the bug is simple for me :
1- Create a score with some notes. Tempo is 100
2- Right click on tempo and click on tempo properties
3- I check "determine tempo from text".
4- I edit the text and wirte 170 instead of 100
5-go to tempo propoerties, I change tempo to 170 (great !)
6- Click on play, tempo is still 100 in the playback
7- Go back once again in tempo properties, uncheck the "determine tempo from text"
8- Click play, the tempo has changed to 170 !

Hope it can help....