global: start relying on file_lock_free(NULL) being a no-op

Cleanup performed with the following semantic patch:

	@@
	expression E;
	@@

	- if (E != NULL) {
	-       file_lock_free(&E);
	- }
	+ file_lock_free(&E);

src/lib-index/mail-cache.c

@@ -91,8 +91,7 @@ void mail_cache_file_close(struct mail_cache *cache)
 	cache->mmap_length = 0;
 	cache->last_field_header_offset = 0;
 
-	if (cache->file_lock != NULL)
-		file_lock_free(&cache->file_lock);
+	file_lock_free(&cache->file_lock);
 	cache->locked = FALSE;
 
 	if (cache->fd != -1) {

src/lib-storage/index/index-mailbox-size.c

@@ -225,8 +225,7 @@ void index_mailbox_vsize_update_deinit(struct mailbox_vsize_update **_update)
 
 	if (update->lock != NULL || update->rebuild)
 		index_mailbox_vsize_update_write(update);
-	if (update->lock != NULL)
-		file_lock_free(&update->lock);
+	file_lock_free(&update->lock);
 	if (update->finish_in_background)
 		index_mailbox_vsize_notify_indexer(update->box);
 

src/lib-storage/mail-autoexpunge.c

@@ -222,7 +222,6 @@ unsigned int mail_user_autoexpunge(struct mail_user *user)
 				break;
 		}
 	}
-	if (lock != NULL)
-		file_lock_free(&lock);
+	file_lock_free(&lock);
 	return expunged_count;
 }

src/lib/file-lock.c

@@ -406,8 +406,7 @@ static void file_try_unlink_locked(struct file_lock *lock)
 		/* nobody was waiting on the lock - unlink it */
 		i_unlink(lock->path);
 	}
-	if (temp_lock != NULL)
-		file_lock_free(&temp_lock);
+	file_lock_free(&temp_lock);
 }
 
 void file_lock_free(struct file_lock **_lock)

src/plugins/fts-squat/squat-trie.c

@@ -1703,17 +1703,15 @@ static int squat_trie_write(struct squat_trie_build_context *ctx)
 
 	if (ret < 0) {
 		i_unlink_if_exists(path);
-		if (file_lock != NULL)
-			file_lock_free(&file_lock);
+		file_lock_free(&file_lock);
 	} else {
 		squat_trie_close_fd(trie);
 		trie->fd = fd;
 		trie->locked_file_size = trie->hdr.used_file_size;
 		if (trie->file_cache != NULL)
 			file_cache_set_fd(trie->file_cache, trie->fd);
 
-		if (ctx->file_lock != NULL)
-			file_lock_free(&ctx->file_lock);
+		file_lock_free(&ctx->file_lock);
 		ctx->file_lock = file_lock;
 	}
 	return ret;

src/plugins/fts-squat/squat-uidlist.c

@@ -553,8 +553,7 @@ static void squat_uidlist_close(struct squat_uidlist *uidlist)
 	squat_uidlist_unmap(uidlist);
 	if (uidlist->file_cache != NULL)
 		file_cache_free(&uidlist->file_cache);
-	if (uidlist->file_lock != NULL)
-		file_lock_free(&uidlist->file_lock);
+	file_lock_free(&uidlist->file_lock);
 	if (uidlist->dotlock != NULL)
 		file_dotlock_delete(&uidlist->dotlock);
 	i_close_fd_path(&uidlist->fd, uidlist->path);