Check all array insertions to prevent adding a nil value

[kas-kad]

Check all array insertions to prevent adding a nil value

[kas-kad]

https://github.com/purrrminator/AdvancedNSOperations/blob/master/Operations/Operations/KADOperation.m#L178

[hamdshah]

@purrrminator gr8 job man, i had started to convert the project to objective-c but then in the middle i found this :smiley:

"internalErrors" is not initialized which caused nil error array on finished.

https://github.com/purrrminator/AdvancedNSOperations/blob/master/Operations/Operations/KADOperation.m#L221

temporary initialization added to "willEnqueue" in my project.