fix assert

Author: shadchin

Objects/unicodeobject.c

@@ -1429,8 +1429,8 @@ _copy_characters(PyObject *to, Py_ssize_t to_start,
     assert(PyUnicode_Check(from));
     assert(from_start + how_many <= PyUnicode_GET_LENGTH(from));
 
-    assert((to == NULL && how_many == 0) || PyUnicode_Check(to));
-    assert((to == NULL && how_many == 0) || (to_start + how_many <= PyUnicode_GET_LENGTH(to)));
+    assert(to == NULL || PyUnicode_Check(to));
+    assert(how_many == 0 || (to_start + how_many <= PyUnicode_GET_LENGTH(to)));
 
     if (how_many == 0)
         return 0;