code: @Override
      public void visitClassContext(ClassContext classContext) {
          try {
              if (exceptionClass != null) {
                  stack = new OpcodeStack();
                  super.visitClassContext(classContext);
              }
          } finally {
              stack = null;
          }
      }
docs: overrides the visitor to initialize and tear down the opcode stack
  
  @param classContext
  the context object of the currently parsed class