tree schema UPDATE terminate enabled features with NULL

So that the array has the same format as arrays
of features in the API.

Author: michalvasko

src/schema_compile.c

@@ -1730,6 +1730,10 @@ lys_compile_enabled_features(struct lys_module *mod)
         }
     }
 
+    /* last NULL feature */
+    LY_ARRAY_NEW_GOTO(mod->ctx, mod->compiled->features, feat_p, rc, cleanup);
+    LY_ARRAY_DECREMENT(mod->compiled->features);
+
 cleanup:
     return rc;
 }

src/tree_schema.h

@@ -1750,7 +1750,8 @@ struct lysc_submodule {
 struct lysc_module {
     struct lys_module *mod;             /**< covering module structure */
 
-    const char **features;              /**< array of all the enabled features ([sized array](@ref sizedarrays)) */
+    const char **features;              /**< array of all the enabled features ([sized array](@ref sizedarrays)), but
+                                             also terminated by NULL */
     struct lysc_node *data;             /**< list of module's top-level data nodes (linked list) */
     struct lysc_node_action *rpcs;      /**< first of actions nodes (linked list) */
     struct lysc_node_notif *notifs;     /**< first of notifications nodes (linked list) */