Early detection out-of-bounds page numbers on the direct-overflow-read

optimization gives consistent error messages regardless of whether or not
the optimization is enabled.

FossilOrigin-Name: b517a52fa36df0a0854a75858b5e81861771d2e9032a5a0ad79aa76ae64130a2

src/btree.c

@@ -4879,6 +4879,7 @@ static int accessPayload(
           assert( aWrite>=pBufStart );                         /* due to (6) */
           memcpy(aSave, aWrite, 4);
           rc = sqlite3OsRead(fd, aWrite, a+4, (i64)pBt->pageSize*(nextPage-1));
+          if( rc && nextPage>pBt->nPage ) rc = SQLITE_CORRUPT_BKPT;
           nextPage = get4byte(aWrite);
           memcpy(aWrite, aSave, 4);
         }else