rcxml.c: fix mem leak when deduplicating keybinds

Before this patch `keybind->keysyms` wasn't free'd when
- deduplicating keybinds
- removing keybinds due to empty action list

This patch creates a shared `keybind_destroy()` helper
which gets used in all cases where a keybind is destroyed.

include/config/keybind.h

@@ -30,6 +30,8 @@ struct keybind {
  */
 struct keybind *keybind_create(const char *keybind);
 
+void keybind_destroy(struct keybind *keybind);
+
 /**
  * parse_modifier - parse a string containing a single modifier name (e.g. "S")
  * into the represented modifier value. returns 0 for invalid modifier names.

src/config/keybind.c

@@ -188,3 +188,12 @@ keybind_create(const char *keybind)
 	wl_list_init(&k->actions);
 	return k;
 }
+
+void
+keybind_destroy(struct keybind *keybind)
+{
+	assert(wl_list_empty(&keybind->actions));
+
+	zfree(keybind->keysyms);
+	zfree(keybind);
+}

src/config/rcxml.c

@@ -1626,7 +1626,7 @@ deduplicate_key_bindings(void)
 			if (keybind_the_same(existing, current)) {
 				wl_list_remove(&existing->link);
 				action_list_free(&existing->actions);
-				free(existing);
+				keybind_destroy(existing);
 				replaced++;
 				break;
 			}
@@ -1635,7 +1635,7 @@ deduplicate_key_bindings(void)
 	wl_list_for_each_safe(current, tmp, &rc.keybinds, link) {
 		if (wl_list_empty(&current->actions)) {
 			wl_list_remove(&current->link);
-			free(current);
+			keybind_destroy(current);
 			cleared++;
 		}
 	}
@@ -1948,8 +1948,7 @@ rcxml_finish(void)
 	wl_list_for_each_safe(k, k_tmp, &rc.keybinds, link) {
 		wl_list_remove(&k->link);
 		action_list_free(&k->actions);
-		zfree(k->keysyms);
-		zfree(k);
+		keybind_destroy(k);
 	}
 
 	struct mousebind *m, *m_tmp;