Don't test mbedtls_mpi_core_lt_ct with 0 limbs
A core MPI must have at least 1 limb. We can no longer test with 0 limbs,
and we don't need to anyway, so don't try.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/library/constant_time_internal.h b/library/constant_time_internal.h
index 9cc63c2..1e4a3ab 100644
--- a/library/constant_time_internal.h
+++ b/library/constant_time_internal.h
@@ -138,6 +138,7 @@
* \param B The right-hand MPI. This must point to an array of limbs
* with the same allocated length as \p A.
* \param limbs The number of limbs in \p A and \p B.
+ * This must not be 0.
*
* \return The result of the comparison:
* \c 1 if \p A is less than \p B.