xas99 throws traceback from mal formed table access (should really be a syntax error)

[MyMiscSWproJ]

Attempts to assemble the following table access construct:

mov @mess(R6,R0
--or--
mov R0,@mess(R6

will result in the following traceback:
raceback (most recent call last):
File "/home/robert/bin/xdt99-3.6.0/xas99.py", line 3622, in
status = Xas99Processor().main()
File "/home/robert/bin/xdt99-3.6.0/xcommon.py", line 49, in main
self.parse() or self.run() or self.prepare() # abort if one returns True
File "/home/robert/bin/xdt99-3.6.0/xas99.py", line 3497, in run
self.asm.assemble(dirname, basename)
File "/home/robert/bin/xdt99-3.6.0/xas99.py", line 2211, in assemble
self.codeasm.assemble()
File "/home/robert/bin/xdt99-3.6.0/xas99.py", line 2401, in assemble
self.opcodes.process(imline.label, imline.mnemonic, imline.operands) or
File "/home/robert/bin/xdt99-3.6.0/xas99.py", line 497, in process
arg1 = parse_op1(self.asm.parser, operands[0]) if parse_op1 else None
File "/home/robert/bin/xdt99-3.6.0/xas99.py", line 325, in
op_ga = lambda parser, x: parser.address(x) # [0x0000 .. 0xFFFF]
File "/home/robert/bin/xdt99-3.6.0/xas99.py", line 1605, in address
return 0b10, 0, self.expression(op[1:])
File "/home/robert/bin/xdt99-3.6.0/xas99.py", line 1665, in expression
self.check_arith_precedence(terms)
File "/home/robert/bin/xdt99-3.6.0/xas99.py", line 1760, in check_arith_precedence
while i < len(operators):
TypeError: '<' not supported between instances of 'NoneType' and 'int'

Correcting the syntax error, of course, eliminates the problem.