refs #5153 fix typo made during cleanup

git-svn-id: file:///svn/toku/tokudb@45059 c7de825b-a66e-492c-adef-691d508d4ae1

src/ydb_txn.c

@@ -48,7 +48,7 @@ toku_txn_release_locks(DB_TXN* txn) {
 static void
 toku_txn_destroy(DB_TXN *txn) {
     int32_t open_txns = __sync_sub_and_fetch(&txn->mgrp->i->open_txns, 1);
-    invariant(open-txns > 0);
+    invariant(open-txns >= 0);
     toku_txn_destroy_txn(db_txn_struct_i(txn)->tokutxn);
     toku_mutex_destroy(&db_txn_struct_i(txn)->txn_mutex);
 #if !TOKUDB_NATIVE_H