Bug #133222 for iCal-Parser: Specifying start sometimes causing recurring events to be lost

When the attached calendar file is parsed using iCal::Parser with no options, it parses the calendar into a bunch of recurring events going years into the future. However, when a "start" option of "20200801" is specified, it doesn't parse the calendar into /any/ events, despite the fact that there are definitely events going into the future that it should return. The problem appears to be that this line in Parser.pm breaks the set: $set=$set->intersection($self->{span}) if $self->{span}; When "start" is set to "20200801", after the line above is executed, evaluating $set->count prints this: Can't call method "is_infinite" on an undefined value at /usr/share/perl5/DateTime/Set.pm line 658, <GEN0> line 47. I can't figure out why so I don't know the correct fix, but I did figure out a workaround, which is shown in the attached patch. In addition, I noticed while debugging this that the code immediately above it constructs $exset but then doesn't use it. I've included in my patch what I believe to be the correct fix for this as well.   Jonathan Kamens