Fermata duration is doubling every time midi is rendered

ee0b1b889d

• Create a score for flute solo
• Add two half notes and a fermata on the second one
• Change fermata "Time stretch" to 2.0
• Play the score, fermata sounds ok
• Change the pitch of the first note to trigger a new rendermidi
• Play again, fermata is twice longer

Choose priority major because it's quite easy to get locked with a very very long fermata.