undo changes from #101 and fix the actual cause

Author: stutrek

Diff for: index.ts

@@ -14,8 +14,8 @@ const scrollMonitor = new ScrollMonitorContainer(
 if (isInBrowser) {
     scrollMonitor.updateState();
     scrollMonitor.listenToDOM();
+    //@ts-ignore
+    window.scrollMonitor = scrollMonitor;
 }
-//@ts-ignore
-window.scrollMonitor = scrollMonitor;
 
 export default scrollMonitor;

Diff for: src/container.ts

@@ -6,11 +6,8 @@ function getViewportHeight(element: HTMLElement) {
     if (isOnServer) {
         return 0;
     }
-    if(typeof window !== 'undefined'){
-        return window.innerHeight;
-    }
     if (element === document.body) {
-        return document.documentElement.clientHeight;
+        return window.innerHeight || document.documentElement.clientHeight;
     } else {
         return element.clientHeight;
     }