prerelease crashes when opening file from 0.9.4

If you open Martineroofblues.msc using a prerelease version of MuseScore then MuseScore crashes.

Workaround: Open the same file using version 0.9.4 and remove the following instruments: drumset, double bass, piano, and 2nd Tenor Saxophone. Save the file and reopen in prerelease version of MuseScore. The file no longer crashes.

I haven't worked out what it is about these four instruments that causes the prereleaes to crash but I noticed that the Tenor Saxophone 2 does not have a time signature.