fix previously untested __Pyx_UnicodeContainsUCS4() implementation for PEP 393

Cython/Compiler/ExprNodes.py

@@ -7016,9 +7016,10 @@ static CYTHON_INLINE int __Pyx_UnicodeContainsUCS4(PyObject* unicode, Py_UCS4 ch
 #ifdef CYTHON_PEP393_ENABLED
     Py_ssize_t i;
     const int kind = PyUnicode_KIND(unicode);
+    const void* udata = PyUnicode_DATA(unicode);
     const Py_ssize_t length = PyUnicode_GET_LENGTH(unicode);
     for (i=0; i < length; i++) {
-        if (unlikely(uchar == PyUnicode_READ(kind, unicode, i))) return 1;
+        if (unlikely(character == PyUnicode_READ(kind, udata, i))) return 1;
     }
     return 0;
 #else