check if the content and the wrapper exists before computing the sizes

package.json

@@ -73,4 +73,4 @@
     "url": "https://github.com/souhe/reactScrollbar/issues"
   },
   "homepage": "https://github.com/souhe/reactScrollbar"
-}
+}

src/js/ScrollArea.jsx

@@ -30,9 +30,9 @@ export default class ScrollArea extends React.Component {
         };
 
         this.scrollArea = {
-            refresh: () => {
-                this.setSizesToState();
-            },
+             refresh: () => {
+                 this.setSizesToState();
+                 },
             scrollTop: () => {
                 this.scrollTop();
             },
@@ -370,10 +370,10 @@ export default class ScrollArea extends React.Component {
     }
 
     computeSizes() {
-        let realHeight = this.content.offsetHeight;
-        let containerHeight = this.wrapper.offsetHeight;
-        let realWidth = this.content.offsetWidth;
-        let containerWidth = this.wrapper.offsetWidth;
+        let realHeight = (this.content) ? this.content.offsetHeight : 0;
+        let containerHeight = (this.wrapper) ? this.wrapper.offsetHeight : 0;
+        let realWidth = (this.content) ? this.content.offsetWidth : 0;
+        let containerWidth = (this.content) ? this.wrapper.offsetWidth : 0;
 
         return {
             realHeight: realHeight,