M http.go → http.go

@@ -142,7 +142,7 @@ renderError(w, InternalServerErrorMsg, 500)
 			return
 		}
 		newName := filepath.Clean(r.Form.Get("rename"))
-		err := checkIfValidFile(newName, fileBytes)
+		err = checkIfValidFile(newName, fileBytes)
 		if err != nil {
 			log.Println(err)
 			renderError(w, err.Error(), 400)