output/filestore: fix coverity issue 1427652

Fix PathMerge error handling bringing back CID 1427652.

The result doesn't need to be checked as we're already in an error state
and the path is only used to print to the user.

src/output-filestore.c

@@ -257,8 +257,7 @@ static int OutputFilestoreLogger(ThreadVars *tv, void *thread_data, const Packet
             /* construct tmp file path */
             char tmp_filename[PATH_MAX] = "";
             snprintf(tmp_filename, sizeof(tmp_filename), "file.%u", ff->file_store_id);
-            if (PathMerge(filename, sizeof(filename), ctx->tmpdir, tmp_filename) < 0)
-                return -1;
+            (void)PathMerge(filename, sizeof(filename), ctx->tmpdir, tmp_filename);
             StatsIncr(tv, aft->fs_error_counter);
             WARN_ONCE(WOT_WRITE, "Filestore (v2) failed to write to %s: %s", filename,
                     strerror(errno));