swaynag: statically allocate button_close, and move declaration

Every swaynag has a close button, so it doesn't make sense to
allocate it dynamically. The declaration is moved later to when
it is actually needed.

swaynag/main.c

@@ -30,16 +30,6 @@ int main(int argc, char **argv) {
 	wl_list_init(&swaynag.outputs);
 	wl_list_init(&swaynag.seats);
 
-	struct swaynag_button *button_close =
-		calloc(sizeof(struct swaynag_button), 1);
-	if (!button_close) {
-		perror("calloc");
-		return EXIT_FAILURE;
-	}
-	button_close->text = strdup("X");
-	button_close->type = SWAYNAG_ACTION_DISMISS;
-	list_add(swaynag.buttons, button_close);
-
 	char *config_path = NULL;
 	bool debug = false;
 	int launch_status = swaynag_parse_options(argc, argv, NULL, NULL, NULL,
@@ -100,6 +90,11 @@ int main(int argc, char **argv) {
 
 	swaynag_types_free(types);
 
+	struct swaynag_button button_close = { 0 };
+	button_close.text = strdup("X");
+	button_close.type = SWAYNAG_ACTION_DISMISS;
+	list_add(swaynag.buttons, &button_close);
+
 	if (swaynag.details.message) {
 		list_add(swaynag.buttons, &swaynag.details.button_details);
 	}