CoreAE: fix invalid logging about mixing matrix
CoreAE: mixing unit must have same output count as mixing map
CoreAE: fix null dereference if no mixer map was created
CoreAE: mixerunits input is the inputunits output

Not this still doesn't resolve all issues. We are still not
setting up a correct channel map for the output
Merge pull request #2581 from Memphiz/frodo_aefixes

[CA/AE] - fixes