HPCC-9028 Roxie not handling OPT flag correctly on dynamically-resolved files

If OPT is specified on a dynamically-resolved file in Roxie, then it is liable
to core if the file cannot be resolved.

Other cases may incorrectly throw an exception when a file is not resolved,
rather than ignoring it as should be done with ,OPT files.

Signed-off-by: Richard Chapman <rchapman@hpccsystems.com>