Add unselect to node and edge

frontend/src/components/Diagram.jsx

@@ -323,12 +323,17 @@ function Diagram() {
         onNodeClick={onNodeClick}
         onNodeDoubleClick={handleNodeDoubleClick}
         onEdgeClick={onEdgeClick}
+        onPaneClick={() => {
+          setSelectedNode(null);
+          setSelectedEdge(null);
+        }}
         nodeTypes={nodeTypes}
         fitView
       >
         <Background />
         <Controls />
       </ReactFlow>
+
     </div>
   );
 }