Layout changes

src/App.css

@@ -21,5 +21,6 @@
 }
 
 .AppContent {
+  height: calc(100% - 36px);
   box-sizing: border-box;
 }

src/App.js

@@ -134,7 +134,7 @@ class App extends IPCContainer {
     let mainContent = [];
     if (this.props.DisplaySelectAppPlatform || !this.props.AppReady) {
       mainContent = (
-        <Box>
+        <Box dxStyle={{height: '100%'}}>
           <Loading/>
         </Box>);
     } else {