Simplify viewportComponent map

platform/viewer/src/components/ViewportGrid.jsx

@@ -84,29 +84,11 @@ function ViewerViewportGrid(props) {
 
     for (let i = 0; i < numViewportPanes; i++) {
       const viewportIndex = i;
-      const paneMeta = viewports[i];
+      const paneMetadata = viewports[i] || {};
-      const isEmpty = !paneMeta || !paneMeta.displaySetInstanceUID;
+      const { displaySetInstanceUID } = paneMetadata;
-
+      const displaySet = DisplaySetService.getDisplaySetByUID(displaySetInstanceUID) || {};
-      if (isEmpty) {
-        viewportPanes[i] = (
-          <ViewportPane
-            key={viewportIndex}
-            className="m-1"
-            acceptDropsFor="displayset"
-            onDrop={onDropHandler.bind(null, viewportIndex)}
-            onInteraction={() => { setActiveViewportIndex(viewportIndex); }}
-            isActive={activeViewportIndex === viewportIndex}
-          >
-            <EmptyViewport />
-          </ViewportPane>
-        );
-      } else {
-        const displaySet = DisplaySetService.getDisplaySetByUID(
-          paneMeta.displaySetInstanceUID
-        );
-
       const ViewportComponent =  _getViewportComponent(
-          displaySet,
+        displaySet.SOPClassHandlerId,
         viewportComponents
       );
 
@@ -115,7 +97,7 @@ function ViewerViewportGrid(props) {
           key={viewportIndex}
           className="m-1"
           acceptDropsFor="displayset"
-            onDrop={onDropHandler}
+          onDrop={onDropHandler.bind(null, viewportIndex)}
           onInteraction={() => { setActiveViewportIndex(viewportIndex); }}
           isActive={activeViewportIndex === viewportIndex}
         >
@@ -127,7 +109,6 @@ function ViewerViewportGrid(props) {
         </ViewportPane>
       );
     }
-    }
 
     return viewportPanes;
   };
@@ -154,8 +135,10 @@ ViewerViewportGrid.defaultProps = {
   viewportComponents: [],
 };
 
-function _getViewportComponent(displaySet, viewportComponents) {
+function _getViewportComponent(SOPClassHandlerId, viewportComponents) {
-  const { SOPClassHandlerId } = displaySet;
+  if (!SOPClassHandlerId) {
+    return EmptyViewport;
+  }
 
   for (let i = 0; i < viewportComponents.length; i++) {
     if (