Fix getargs argument passing

Fixes mypyc/mypyc#1078

See python#17930

Author: hauntsaninja

mypyc/lib-rt/getargs.c

@@ -374,8 +374,6 @@ vgetargskeywords(PyObject *args, PyObject *kwargs, const char *format,
             int res = PyDict_GetItemStringRef(kwargs, kwlist[i], &current_arg);
             if (res == 1) {
                 Py_DECREF(current_arg);
-            }
-            else if (unlikely(res == 0)) {
                 /* arg present in tuple and in dict */
                 PyErr_Format(PyExc_TypeError,
                              "argument for %.200s%s given by name ('%s') "

mypyc/test-data/run-classes.test

@@ -467,6 +467,14 @@ a = A(10)
 assert a.foo() == 11
 assert foo() == 21
 
+[case testClassKwargs]
+class X:
+    def __init__(self, msg: str, **variables: int) -> None:
+         pass
+[file driver.py]
+from native import X
+X('hello', a=0)
+
 [case testGenericClass]
 from typing import TypeVar, Generic, Sequence
 T = TypeVar('T')