rpcrt4/tests: Only free string when function succeeded

[André Hentschel]

should fix http://test.winehq.org/data/c1aaacd58c505548351defcb1077c65e8bd59fc3/nt4_fg-winnt4-sp4/rpcrt4:rpc.html
---
 dlls/rpcrt4/tests/rpc.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/dlls/rpcrt4/tests/rpc.c b/dlls/rpcrt4/tests/rpc.c
index 4d62f30..83e387b 100644
--- a/dlls/rpcrt4/tests/rpc.c
+++ b/dlls/rpcrt4/tests/rpc.c
@@ -283,8 +283,7 @@ todo_wine {
     ok(level == RPC_C_AUTHN_LEVEL_PKT_PRIVACY, "expected RPC_C_AUTHN_LEVEL_PKT_PRIVACY, got %d\n", level);
     ok(authnsvc == RPC_C_AUTHN_WINNT, "expected RPC_C_AUTHN_WINNT, got %d\n", authnsvc);
     todo_wine ok(authzsvc == RPC_C_AUTHZ_NAME, "expected RPC_C_AUTHZ_NAME, got %d\n", authzsvc);
-
-    RpcStringFree(&principal);
+    if (status == RPC_S_OK) RpcStringFree(&principal);
 
     status = RpcMgmtStopServerListening(NULL);
     ok(status == RPC_S_OK, "RpcMgmtStopServerListening failed (%u)\n",
-- 

Best Regards, André Hentschel