Remove casting warning

git-svn-id: svn+ssh://svn.code.sf.net/p/mingw-w64/code/trunk@5813 4407c894-4637-0410-b4f5-ada5f102cad1

mingw-w64-libraries/winpthreads/tests/test.c

diff --git a/mingw-w64-libraries/winpthreads/tests/test.c b/mingw-w64-libraries/winpthreads/tests/test.c
index 95c61fd..06e8456 100644
--- a/mingw-w64-libraries/winpthreads/tests/test.c
+++ b/mingw-w64-libraries/winpthreads/tests/test.c
@@ -504,7 +504,7 @@
                     f++;
                     printf("_pthread_tryjoin failed: %d %d %d\n",i, rc,thread[i]->tid);
                 } else {
-                    thread[i] = NULL;
+                    thread[i] = 0;
                     printf("_pthread_tryjoin OK: %d\n",i);
                 }
             }