[FIX] spreadsheet: fix useSpreadsheetRect

The hook `useSpreadsheetRect` was doing a querySelector(".o-spreadsheet")
as soon as it was called, instead of waiting for the `onMounted`.

That meant that when creating a new spreadsheet component after
destroying another, the hook would return the rect of the old
spreadsheet.

closes #4370

Task: 3965147
X-original-commit: 402bf1d
Signed-off-by: Rémi Rahir (rar) <rar@odoo.com>
Signed-off-by: Adrien Minne (adrm) <adrm@odoo.com>

src/components/helpers/position_hook.ts

@@ -10,8 +10,7 @@ type Ref = ReturnType<typeof useRef>;
  */
 export function useSpreadsheetRect(): Rect {
   const position = useState({ x: 0, y: 0, width: 0, height: 0 });
-  let spreadsheetElement = document.querySelector(".o-spreadsheet");
-  updatePosition();
+  let spreadsheetElement: Element | null = null;
   function updatePosition() {
     if (!spreadsheetElement) {
       spreadsheetElement = document.querySelector(".o-spreadsheet");