Fix issue 9852.

_aaEqual should not dereference null when given a null AA.
Merge pull request #541 from quickfur/issue9852

Fix issue 9852.
Supplemental fix for issue 10567

Add helper function in druntime, same as opEquals case.
Merge pull request #543 from 9rnsr/fix10567

Supplemental fix for issue 10567