Query table error when input contains [ and ]

[Dylan C]

When using a query table with a check for a value containing [] causes the test to be interrupted.
When we have a query parameter of "[broadcast]" in our forth column of the query table the following stack trace occurs in the error log for the test page.

Traceback (most recent call last):
  File ".../waferslim/server.py", line 56, in handle
    received, sent = self.respond_to_request(isolate_imports=SlimRequestHandler.ISOLATE_IMPORTS)
  File ".../waferslim/protocol.py", line 135, in respond_to_request
    results)
  File ".../waferslim/protocol.py", line 166, in _message_loop
    instruction_list = instructions(unpack(message))
  File ".../waferslim/protocol.py", line 44, in unpack
    _unpack_chunk(packed_string, chunks)
  File ".../waferslim/protocol.py", line 67, in _unpack_chunk
    _unpack_chunk(item, sub_chunk)
  File ".../waferslim/protocol.py", line 67, in _unpack_chunk
    _unpack_chunk(item, sub_chunk)
  File ".../waferslim/protocol.py", line 67, in _unpack_chunk
    _unpack_chunk(item, sub_chunk)
  File ".../waferslim/protocol.py", line 67, in _unpack_chunk
    _unpack_chunk(item, sub_chunk)
  File ".../waferslim/protocol.py", line 52, in _unpack_chunk
    chunk_len = int(packed_chunk[pos:pos + _NUMERIC_LENGTH])
ValueError: invalid literal for int() with base 10: 'broadc'