Ignore Error in Calling Class

Hi,

I call a class which in turn inherits an API class. That class calls another class which returns a value.

Class1 calls Class2.

Class2 inherits Class3.

Class3 calls Class4 that returns a value. The input to return the value is null. However, Class3 and Class4 are wrapped in an API. So you cant edit it.So it throws an error in Class1. How do I ignore this error?

Thanks