[libglnx] tests: Fix a -Wmaybe-uninitialized warning

[Colin Walters <walters src gnome org>]

commit ea6df95f22c8f2973714bdbb8b1accc4e37d4d56
Author: Colin Walters <walters verbum org>
Date:   Fri Jul 21 18:08:23 2017 -0400

    tests: Fix a -Wmaybe-uninitialized warning
    
    It'd be really nice if gtest had a variant which had the funcs take `GError`.
    May work on that.

 tests/test-libglnx-fdio.c |    9 ++++++++-
 1 files changed, 8 insertions(+), 1 deletions(-)
---
diff --git a/tests/test-libglnx-fdio.c b/tests/test-libglnx-fdio.c
index d4e6272..16b6692 100644
--- a/tests/test-libglnx-fdio.c
+++ b/tests/test-libglnx-fdio.c
@@ -166,10 +166,17 @@ test_stdio_file (void)
   g_autoptr(GError) local_error = NULL;
   GError **error = &local_error;
   g_auto(GLnxTmpfile) tmpf = { 0, };
+  g_autoptr(FILE) f = NULL;
+
   if (!glnx_open_anonymous_tmpfile (O_RDWR|O_CLOEXEC, &tmpf, error))
     goto out;
+  f = fdopen (tmpf.fd, "w");
+  if (!f)
+    {
+      (void)glnx_throw_errno_prefix (error, "fdopen");
+      goto out;
+    }
 
-  g_autoptr(FILE) f = fdopen (tmpf.fd, "w");
   if (fwrite ("hello", 1, strlen ("hello"), f) != strlen ("hello"))
     {
       (void)glnx_throw_errno_prefix (error, "fwrite");