Adds one last input guard.

Author: chaburkland

src/_arraykit.c

@@ -619,6 +619,11 @@ get_new_indexers_and_screen(PyObject *Py_UNUSED(m), PyObject *args, PyObject *kw
         return NULL;
     }
 
+    if (PyArray_NDIM(positions) != 1) {
+        PyErr_SetString(PyExc_ValueError, "positions must be 1-dimensional");
+        return NULL;
+    }
+
     if (PyArray_TYPE(indexers) != NPY_INT64) {
         PyErr_SetString(PyExc_ValueError, "Array must be of type np.int64");
         return NULL;

test/test_util.py

@@ -427,6 +427,9 @@ def test_get_new_indexers_and_screen_b(self) -> None:
         with self.assertRaises(ValueError):
             get_new_indexers_and_screen(indexersA.astype(np.int32), np.arange(5))
 
+        with self.assertRaises(ValueError):
+            get_new_indexers_and_screen(indexersA, np.arange(5).astype(np.int32))
+
         indexersB = np.arange(25, dtype=np.int64)
         postB = get_new_indexers_and_screen(indexersB, indexersB)
         assert tuple(map(list, postB)) == (list(indexersB), list(indexersB))