Guardian Portal read access for Sales Invoice

[Manioke]

Theres currently a issue with the education module where if i login as a guardian to the edu-portal i can't view the students Fees because the guardian doesn't have read permissions for the sales invoice doctype.

[tuwafula]

Hello, the issue has been fixed. Refer to PR #481 if you're on version-15.2 or PR #482 if you're on version-16