Fix URL null error when no url is given in event

src/models/calendar/events/icalgenerator.service.ts

@@ -39,7 +39,9 @@ const serializeIcalEvent = (icalevent: iCalEvent): string => {
 	returnString += 'SUMMARY:' + icalevent.summary;
 	returnString += 'DESCRIPTION:' + icalevent.description;
 	returnString += 'LOCATION:' + icalevent.location;
-	returnString += 'URL:' + icalevent.url;
+	if(!isNullOrBlank(icalevent.url)) {
+		returnString += 'URL:' + icalevent.url;
+	}
 	returnString += icalevent.footer;
 
 	return returnString;
@@ -82,6 +84,8 @@ const addEventToFile = (ical: iCalFile, event: Event) => {
 };
 
 const createIcalEvent = (event: Event): iCalEvent => {
+	let url = event.url ? event.url + '\n' : '';
+
 	return {
 		header: 'BEGIN:VEVENT\n',
 		uid: event.uuid + '\n',
@@ -92,7 +96,7 @@ const createIcalEvent = (event: Event): iCalEvent => {
 		summary: event.name + '\n',
 		description: event.description + '\n',
 		location: event.location + '\n',
-		url: event.url + '\n',
+		url: url,
 		footer: 'END:VEVENT\n'
 	};
 };
@@ -130,3 +134,11 @@ export interface iCalEvent {
 	url: string;
 	footer: string;
 }
+
+/**
+ * Checks if a given string is null, undefined or blank
+ * @param str The string to check
+ */
+function isNullOrBlank(str: string | null): boolean {
+	return str === null || str === undefined || str.trim() === '';
+}