crypt32/tests: Prevent a crash on Win9x (test_data_msg).

dlls/crypt32/tests/msg.c

@@ -413,9 +413,12 @@ static void test_data_msg_update(void)
     ok(ret, "CryptMsgUpdate failed: %x\n", GetLastError());
     CryptMsgClose(msg);
 
+    if (have_nt)
+    {
         /* Calling update after opening with an empty stream info (with a bogus
          * output function) yields an error:
          */
+        /* Crashes on some Win9x */
         msg = CryptMsgOpenToEncode(PKCS_7_ASN_ENCODING, 0, CMSG_DATA, NULL, NULL,
          &streamInfo);
         SetLastError(0xdeadbeef);
@@ -425,6 +428,7 @@ static void test_data_msg_update(void)
          "Expected STATUS_ACCESS_VIOLATION or STATUS_ILLEGAL_INSTRUCTION, got %x\n",
          GetLastError());
         CryptMsgClose(msg);
+    }
     /* Calling update with a valid output function succeeds, even if the data
      * exceeds the size specified in the stream info.
      */