workspace overview cluster list grows/shrinks according to existence of extension details

Signed-off-by: Jim Ehrismann <jehrismann@mirantis.com>

src/renderer/components/+landing-page/workspace-overview.scss

@@ -1,4 +1,5 @@
 .WorkspaceOverview {
+  height: 100%;
 
   .ItemListLayout.WorkspaceClusters {
     background-color: var(--mainBackground);

src/renderer/components/+landing-page/workspace-overview.tsx

@@ -38,7 +38,7 @@ export class WorkspaceOverview extends Component<Props> {
     return (
       <div className="WorkspaceOverview flex column gaps box grow">
         <ItemListLayout 
-          className="WorkspaceClusters"
+          className="WorkspaceClusters box grow"
           renderHeaderTitle={<div>Clusters</div>}
           isClusterScoped
           isSearchable={false}
@@ -66,11 +66,14 @@ export class WorkspaceOverview extends Component<Props> {
             <WorkspaceClusterMenu clusterItem={clusterItem} workspace={workspace} workspaceClusterStore={workspaceClusterStore}/>
           )}
         />
-        { workspaceDetails.length > 0 && 
+        { workspaceDetails.length > 0 && (
+          <>
+            <hr/>
             <div className="extensions flex column gaps">
               {workspaceDetailRegistry.getItems().map(({ components: { Detail } }, index) => <Detail key={index} className="workspace-detail"/>)}
             </div>
-        }
+          </>
+        )}
       </div>
     );
   }