Fix null -> nullptr in CppInterOp.cpp

Author: alexander-penev

lib/Interpreter/CppInterOp.cpp

@@ -67,7 +67,7 @@ namespace Cpp {
   // Last assigned Autoload SearchGenerator
   // TODO: Test fot thread safe.
   class AutoLoadLibrarySearchGenerator;
-  static AutoLoadLibrarySearchGenerator *sAutoSG = null;
+  static AutoLoadLibrarySearchGenerator *sAutoSG = nullptr;
   // Flag to indicate ownership when an external interpreter instance is used.
   static bool OwningSInterpreter = true;
   static compat::Interpreter* sInterpreter = nullptr;