Make sure superclass isn't nil
I was attempting to use mocks and ran into this issue
In lib/spectator/src/spectator/mocks/stubs.cr:45:37
45 | (t.superclass.has_method?(name) && !t.overrides?(t.superclass, name))
^----------
Error: undefined macro method 'NilLiteral#has_method?'
it was easily solved by just checking that t.superclass
is not nil.