exp-meta-linear-rules assertion error

[sligocki]

Some folks have been noticing this cryptic assertion error when running with --exp-meta-linear-rules

> Code/Quick_Sim.py 1RB0RG_0LC1RE_---1RD_1LE1LF_1RF0LD_0LC1RA_1RA0LB -r --exp-linear-rules --exp-meta-linear-rules --block-mult=2 --no-steps
...
  File "/Users/sl929/fun/bb/busy-beaver/Code/Exp_Int.py", line 507, in __ge__
    assert is_const(self), self
           ~~~~~~~~^^^^^^
AssertionError: (350 + 3^(<x34> + 1048583) + 3^(9 <x34> + (9437224 + 3^(<x34> + 1048581))))