M36 with a filename doesn't return the customInfo if a print job is running

[dc42]

In RRF 3.6.0 post beta 4 if M36 is used with a filename parameter, the contexts of any customInfo comments in the file are normally included in the output. However it does not include the custom info if a job is being run, instead it reports "customInfo":{}. It makes no difference if the print is paused. M36 without a filename parameter does report the customInfo for the job currently running.

[dc42]

It isn't just the customInfo that is missing, other parts of the info may be missing too. The reason is that RepRap::GetFileInfoResponse in general makes multiple calls to FileInfoParser::GetFileInfo (via MassStorage::GetFileInfo) until it doesn't return GCodeResult::notFinished, but it passes empty GCodeFileInfo and GlobalVariables objects each time. When no file is being printed, FileInfoParser::GetFileInfo loops internally for faster response so it usually completes in a single call; but when a file is being printed it doesn't so as to avoid disturbing the file being printed. A solution would be to allocate GCodeFileInfo and GlobalVariables objects before making the calls, and free them afterwards. Or perhaps have a single static instance of each and a mutex to protect them.