Explicitly allow NULL as an argument to mbedtls_ccm_free()
diff --git a/include/mbedtls/ccm.h b/include/mbedtls/ccm.h
index 0eb1abe..6210c1f 100644
--- a/include/mbedtls/ccm.h
+++ b/include/mbedtls/ccm.h
@@ -109,7 +109,9 @@
* \brief This function releases and clears the specified CCM context
* and underlying cipher sub-context.
*
- * \param ctx The CCM context to clear. Must not be \c NULL.
+ * \param ctx The CCM context to clear.
+ *
+ * \note If ctx is \c NULL, the function has no effect.
*/
void mbedtls_ccm_free( mbedtls_ccm_context *ctx );