fix crash on rrule.between returned bad dates #3256 (#3257)

Fixes: #3256 

BUT.. the testcase is inconclusive.. as the code FAILS without the fix,
BUT somehow RETURNS 0 entries..
in real life run the node helper fails, and all calendar processing
stops.

tests/configs/modules/calendar/bad_rrule.js

@@ -0,0 +1,27 @@
+/* MagicMirror² Test ics with out of date event causing bad return from rrule.between
+ *
+ * By Sam Detweiler
+ * MIT Licensed.
+ */
+let config = {
+	timeFormat: 12,
+	logLevel: ["INFO", "LOG", "WARN", "ERROR", "DEBUG"],
+	modules: [
+		{
+			module: "calendar",
+			position: "bottom_bar",
+			config: {
+				calendars: [
+					{
+						url: "http://localhost:8080/tests/mocks/bad_rrule.ics"
+					}
+				]
+			}
+		}
+	]
+};
+
+/*************** DO NOT EDIT THE LINE BELOW ***************/
+if (typeof module !== "undefined") {
+	module.exports = config;
+}