sim-rs: fix visualization compilation errors

Author: SupernaviX

ui/src/components/Graph/modules/Canvas.tsx

@@ -23,7 +23,7 @@ export const Canvas: FC = () => {
   } = useSimContext();
   const isDragging = useRef(false);
   const dragStart = useRef({ x: 0, y: 0 });
-  const pointerCapture = useRef<number>();
+  const pointerCapture = useRef<number | undefined>(undefined);
 
   useEffect(() => {
     const canvas = canvasRef.current;

ui/src/contexts/SimContext/SimContextProvider.tsx

@@ -14,7 +14,7 @@ export const SimContextProvider: FC<PropsWithChildren> = ({ children }) => {
   const [state, dispatch] = useReducer(reducer, defaultState);
 
   // load topology
-  const canvasRef = useRef<HTMLCanvasElement>(defaultState.graph.canvasRef.current);
+  const canvasRef = useRef<HTMLCanvasElement | null>(defaultState.graph.canvasRef.current);
   const resolvedState = useMemo(
     () => ({
       ...state,

ui/src/contexts/SimContext/types.ts

@@ -104,7 +104,7 @@ export interface ISimulationIntermediateDataState {
 }
 
 export interface IGraphContextState {
-  canvasRef: RefObject<HTMLCanvasElement>;
+  canvasRef: RefObject<HTMLCanvasElement | null>;
   canvasScale: number;
   canvasOffsetX: number;
   canvasOffsetY: number;