Fatal error editing sequence length

[mbroskamp]

This is a new issue I found when working on a profile for my previous bug report. If you have a sequence without any steps and try to edit the sequence length, you get a fatal error, which causes QLC+ to close.

Version: 4.10.2b
OS: Windows 10

Reproduction steps:

• Open the Show Manager in QLC+
• Add a new sequence
• Open the "Item start time and duration" dialog
• Change one of the duration fields to a value greater than 0

In Windows, you'll get a system dialog saying QLC+ has stopped working and will cause the program to close.