Queued commands not executed causing tool change to hang

[dc42]

We have an example of tool changes hanging because queued commands are not executing. See https://forum.duet3d.com/topic/35641/printer-hanging-during-tool-change-with-v3-5-1.

[T3P3]

suggested workaround that appears to work:

insert a M400 or G4 P0 command before the M98 P"/sys/tconfig0.g" line at the end of tpre0.g

Probably only affects macros that call other macros as the last command.