degesch: fix memory issue in Readline

We didn't zero out the pointer for entries.

degesch.c

@@ -336,6 +336,7 @@ input_restore_buffer (struct input *self, struct input_buffer *buffer)
 		// cleared them altogether, so there should be nothing to leak.
 		HISTORY_STATE *state = history_get_history_state ();
 		state->offset = state->length = state->size = 0;
+		state->entries = NULL;
 		history_set_history_state (state);
 		free (state);
 	}