Fix for optional package_intents
Fix for optional package_intents

Package Intents are optional in STIX, and the original code throws an
exception of the source document does not have this.  Rather than
checking the way it was done, look for the presence of the attribute
and if present, then do the same thing.

jinverar/crits,jhuapl-marti/marti,lakiw/cripts,kaoscoach/crits,kaoscoach/crits,jinverar/crits,blaquee/crits,DukeOfHazard/crits,ckane/crits,lakiw/cripts,seanthegeek/crits,korrosivesec/crits,dreardon/crits,jhuapl-marti/marti,davidhdz/crits,Magicked/crits,cdorer/crits,HardlyHaki/crits,ckane/crits,lakiw/cripts,jinverar/crits,Magicked/crits,lakiw/cripts,jinverar/crits,Lambdanaut/crits,dreardon/crits,DukeOfHazard/crits,Lambdanaut/crits,seanthegeek/crits,jhuapl-marti/marti,Lambdanaut/crits,ckane/crits,HardlyHaki/crits,0x3a/crits,ckane/crits,davidhdz/crits,davidhdz/crits,DukeOfHazard/crits,HardlyHaki/crits,korrosivesec/crits,Lambdanaut/crits,cfossace/crits,cfossace/crits,cfossace/crits,korrosivesec/crits,blaquee/crits,jhuapl-marti/marti,dreardon/crits,0x3a/crits,Magicked/crits,seanthegeek/crits,seanthegeek/crits,HardlyHaki/crits,blaquee/crits,cfossace/crits,0x3a/crits,Magicked/crits,0x3a/crits,DukeOfHazard/crits,cdorer/crits,cdorer/crits,cdorer/crits,kaoscoach/crits,blaquee/crits,davidhdz/crits,korrosivesec/crits,davidhdz/crits,dreardon/crits,seanthegeek/crits,kaoscoach/crits