Remove null assignment.

Null be default.

Author: khatchad

com.ibm.wala.cast.python.jython3/source/com/ibm/wala/cast/python/util/Python3Interpreter.java

@@ -4,7 +4,7 @@
 
 public class Python3Interpreter extends com.ibm.wala.cast.python.util.PythonInterpreter {
 
-  private static PythonInterpreter interp = null;
+  private static PythonInterpreter interp;
 
   public static PythonInterpreter getInterp() {
     try {