Ensure that the sqlite3BtreeLast() interface initializes the *pRes return

to zero if the cursor is already sitting on the last entry of the table.

FossilOrigin-Name: ebe4845cd0ffb96b30be3c69eb399d58e93149886bc2fa60a7ebd7b4fbe447a4

src/btree.c

@@ -5294,6 +5294,7 @@ int sqlite3BtreeLast(BtCursor *pCur, int *pRes){
     assert( pCur->ix==pCur->pPage->nCell-1 );
     assert( pCur->pPage->leaf );
 #endif
+    *pRes = 0;
     return SQLITE_OK;
   }