Mark no input as empty instead of wrong for geometry proofs 1
Mark no input as empty instead of wrong for geometry proofs intro
Fix unstyled MathJax/Katex hint for geometry intro shared problem
Merge branch 'Fix-TriangleProofsEmptyInsteadWrong' of https://github.com/richard-to/khan-exercises

Conflicts:
	exercises/geometry_proofs_1.html