fix(autoclose): browser detection for SSR (#3027)

Fixes #3025

src/util/autoclose.ts

@@ -8,7 +8,11 @@ const isHTMLElementContainedIn = (element: HTMLElement, array?: HTMLElement[]) =
 
 // we'll have to use 'touch' events instead of 'mouse' events on iOS and add a more significant delay
 // to avoid re-opening when handling (click) on a toggling element
-const iOS = !!navigator.userAgent && /iPad|iPhone|iPod/.test(navigator.userAgent);
+// TODO: use proper Angular platform detection when NgbAutoClose becomes a service and we can inject PLATFORM_ID
+let iOS = false;
+if (typeof navigator !== 'undefined') {
+  iOS = !!navigator.userAgent && /iPad|iPhone|iPod/.test(navigator.userAgent);
+}
 
 export function ngbAutoClose(
     zone: NgZone, document: any, type: boolean | 'inside' | 'outside', close: () => void, closed$: Observable<any>,