Fixed issue with GP3 files where a slide starting on a dotted note caused a crash.
Fixed rare crash in GP3 files created by TG where very high notes are specified.

TuxGuitar allows users to specify notes which are extremely high in
pitch, beyond what Guitar Pro can support. Guitar Pro handles problem
by setting the fret number to 0 and displaying the note as intended
(it cannot specify a fret number as there is no fret number which can
create such a pitch). This patch makes MS match the behavior of Guitar
Pro instead of crashing.
Merge pull request #1419 from jpirie/guitar-pro-import

Guitar pro import