efl-mono: Allow generating doc refs for methods without class

efl-mono: Allow generating doc refs for methods without class

Summary:
Methods without a class (global) make the previous code crash because
func.klass contains something (it cannot be NULL because it is a reference)
but you cannot make much calls on this something.

Test Plan: Currently there are no such references, but I need this working for upcoming patches.

Reviewers: lauromoura, vitor.sousa

Reviewed By: vitor.sousa

Subscribers: vitor.sousa, cedric, #reviewers, #committers

Tags: #efl

Differential Revision: https://phab.enlightenment.org/D8585