[minimap] fix #78

On the nodereducer, sometimes the `getNodeDisplayData` returns no value
, even if the node is in the graph. Probably due to the fact that the
node is currently rendering and so in the man time has no render values
...
Adding default values to fix.

Author: sim51

packages/minimap/src/Minimap.tsx

@@ -47,11 +47,14 @@ export const MiniMap: FC<MiniMapProps> = ({ width, height, debounceTime }) => {
    */
   const nodeReducer = useCallback(
     (node: string) => {
-      const data = sigma.getNodeDisplayData(node)!;
+      const data = sigma.getNodeDisplayData(node);
       return {
-        ...data,
+        x: 0,
+        y: 0,
+        ...(data || {}),
         type: 'circle',
-        size: data.size * ratioHeight,
+        size: (data?.size || 1) * ratioHeight,
+        label: undefined,
       };
     },
     [sigma, ratioHeight],