This server parameter and the related code (catchingInvoke) that uses it were used in an attempt to stop throwing from getAsyncs in NetworkInterfaceTL.
Looking at the code now (with the benefit of hindsight), I believe this significantly complicates the code to now useful benefit, and some of the usages may be incorrect. We should remove this code and simply ensure that anything we call from getASync cannot throw, rather than trying to handle it.