node-ical: Uncatchable Exception from rrule

we got a Sentry crash report:

https://sentry.iobroker.net/share/issue/d68908f6a8824381ab4e390108378841/

Error: Unknown RRULE property 'RRULE'
  File "/opt/iobroker/node_modules/rrule/dist/es5/webpack:/rrule/src/parsestring.ts", line 98, col 15, in null.<anonymous>
  ?, in Array.forEach
  File "/opt/iobroker/node_modules/rrule/dist/es5/webpack:/rrule/src/parsestring.ts", line 56, col 9, in parseRrule
  File "/opt/iobroker/node_modules/rrule/dist/es5/webpack:/rrule/src/parsestring.ts", line 42, col 14, in parseLine
  ?, in Array.map
  File "/opt/iobroker/node_modules/rrule/dist/es5/webpack:/rrule/src/parsestring.ts", line 7, col 41, in Function.parseString
  File "/opt/iobroker/node_modules/rrule/dist/es5/webpack:/rrule/src/rrule.ts", line 127, col 28, in Function.RRule.fromString
  File "/opt/iobroker/node_modules/node-ical/ical.js", line 415, col 30, in Object.END
    curr.rrule = rrule.fromString(rule);
  File "/opt/iobroker/node_modules/node-ical/ical.js", line 452, col 39, in Object.handleObject
    return self.objectHandlers[name](val, params, ctx, stack, line);
  File "/opt/iobroker/node_modules/node-ical/ical.js", line 499, col 18, in Object.parseLines
    ctx = self.handleObject(name, value, params, ctx, stack, l) || {};

in fact when I understood correct then https://github.com/jens-maus/node-ical/blob/master/ical.js#L415 can throw an exception … this should be catched because of the “setImmediate” processing that exception is uncatchable else