fix defragment bug

source/libs/tdb/src/page/tdbPage.c

@@ -372,11 +372,11 @@ static int tdbPageDefragment(SPage *pPage) {
   int    idx;
   int    iCell;
 
-  ASSERT(pPage->pFreeEnd - pPage->pFreeStart < nFree);
-
   nFree = TDB_PAGE_NFREE(pPage);
   nCells = TDB_PAGE_NCELLS(pPage);
 
+  ASSERT(pPage->pFreeEnd - pPage->pFreeStart < nFree);
+
   // Loop to compact the page content
   // Here we use an O(n^2) algorithm to do the job since
   // this is a low frequency job.