Fix an assert() in btree to be more precise, as the previous form of that

asser might fail due to recent performance optimizations.

FossilOrigin-Name: 4774938134d0105423720bdc1b4e82164a1e28d993c5cd81c1b03f1f0878427e

src/btree.c

@@ -2309,9 +2309,7 @@ getAndInitPage_error1:
     pCur->pPage = pCur->apPage[pCur->iPage];
   }
   testcase( pgno==0 );
-  assert( pgno!=0 || rc==SQLITE_CORRUPT 
-                  || rc==SQLITE_IOERR_NOMEM
-                  || rc==SQLITE_NOMEM );
+  assert( pgno!=0 || rc!=SQLITE_OK );
   return rc;
 }