Fixed bug which prevents cached FS files from being updated

Bug was introduced in previous "Fixed recompressing of stale files"
commit.

fs.go

@@ -1144,7 +1144,7 @@ func (h *fsHandler) openFSFile(filePath string, mustCompress bool) (*fsFile, err
 		// Only re-create the compressed file if there was more than a second between the mod times.
 		// On MacOS the gzip seems to truncate the nanoseconds in the mod time causing the original file
 		// to look newer than the gzipped file.
-		if fileInfo.ModTime().Sub(fileInfoOriginal.ModTime()) >= time.Second {
+		if fileInfoOriginal.ModTime().Sub(fileInfo.ModTime()) >= time.Second {
 			// The compressed file became stale. Re-create it.
 			f.Close()
 			os.Remove(filePath)