Fix tree support related crash that occurs if there are no overhangs

[ThomasRahm]

Description

Fixes tree support related crash that occurs if there are no overhangs. It also abort tree support generation early if there are no overhangs to support.

Type of change

• [x] Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

• [x] Crash linked in Discussion

Test Configuration:

• Operating System: Windows 10

Checklist:

• [x] My code follows the style guidelines of this project as described in UltiMaker Meta
• [x] I have read the Contribution guide
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have uploaded any files required to test this change

[saumyaj3]

Hey @ThomasRahm Thankyou for your valuable contribution. You make Cura community very happy 👯