py/objslice: Validate that the argument to indices() is an integer.

Otherwise passing in a non-integer can lead to an invalid memory access.

Thanks to Junwha Hong and Wonil Jang @S2Lab, UNIST for finding the issue.

Fixes issue #13007.

Signed-off-by: Damien George <damien@micropython.org>

tests/basics/slice_indices.py

@@ -25,3 +25,8 @@ print(A()[2:7:2].indices(5))
 print(A()[2:7:-2].indices(5))
 print(A()[7:2:2].indices(5))
 print(A()[7:2:-2].indices(5))
+
+try:
+    print(A()[::].indices(None))
+except TypeError:
+    print("TypeError")