multiply_vxx_const.set_k() in GR3.9 seems to be busticated?

[Marcus D. Leech]

This is an apparent problem in 3.9.0.0-git

In grc, create a multiply_const with a vector size > 1

Have a function_probe block that sets the constant on a regular 
basis--perhaps from a variable, or a function call or the like.

The constant will never be updated, even thought the function_probe 
setter is getting called.  It's like the statement that contains the
  muitiply_const_vxx.set_k() is never even getting evaluated, because 
if the value inside the set_k is itself a function call, that function
  is never called.

This caused me to pull my hair out (well, figuratively).

Now the originating flow-graph .grc file originated from GR 3.7 but GRC 
3.9 didn't appear to have any problem converting it and the
  generated python looks entirely valid.  This is almost like Python3 
is simply quietly ignoring the entire statement and I cannot
  understand why.