Null board when creating new puzzle file bug fix

[charlestian23]

Description

Fixed a bug where attempting to save a brand new puzzle file created in LEGUP would cause an error since the length of the proof tree would be 0. This fixes that error by adding an if check to get the puzzle board an alternative way if the length of the proof tree is 0.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Enhancement (improvement to an already existing feature)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

How Has This Been Tested?

Checklist:

• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (if applicable)
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[Chase-Grajeda]

Squashes bug, passed tests