Crash on load of 1.3 score with bad tie (one-sided, extends to end of score)

Windows 7, GIT commit: c20b96e

1) open attached score (created in 1.3)

Result: crash

The crash occurs while laying out a tie. The start element reports it is a note in measure 4, but the end element is a segment (in measure 9) rather than a note, so measure() returns 0, and we crash dereferencing that. Opening the score in 1.3, you can see a corrupt tie there in measure 9. But of course, we should do better than crash.

Still, I'm not bothering to mark this critical, since I find it hard to get worked up about crashes on corrupt input.