UESaveFile: close the file after we're done writing to it.

src/UESaveFile/UESaveFile.cpp

@@ -101,6 +101,8 @@ auto UESaveFile::saveToFile() -> bool {
 
     writer.writeUnsignedInt(0);
 
+    writer.closeFile();
+
     if(!Utility::Directory::copy(_filepath, _filepath + ".bak")) {
         return false;
     }