calling _pfp__set_value on a Struct always raises an exception

[michaelmera]

Describe the bug

Calling fields.Struct._pfp__set_value always results in a NameError exception. This is because of a typo in a variable name in this function.

To Reproduce

Here is a test reproducing the error:

    def test_struct_set_value(self):
        dom = self._test_parse_build(
            "abc",
            """
                typedef struct {
                    char first;
                    char second;
                    char third;
                } three_bytes;

                three_bytes bytes;
            """,
        )

        dom.bytes._pfp__set_value([ord("x"), ord("y"), ord("z")])
        self.assertEqual(dom.bytes.first, ord("x"))
        self.assertEqual(dom.bytes.second, ord("y"))
        self.assertEqual(dom.bytes.third, ord("z"))

resulting in the following error:

Traceback (most recent call last):
  File "pfp/tests/test_struct_union_2.py", line 479, in test_struct_set_value
    dom.bytes._pfp__set_value([ord("x"), ord("y"), ord("z")])
  File "pfp/tests/../pfp/fields.py", line 835, in _pfp__set_value
    return modified_watches
NameError: name 'modified_watches' is not defined

Expected Behavior

Calling _pfp__set_value should replace the current struct value with the argument, overwriting the struct's children.