[glib/wip/pwithnall/io-channel-double-close-source] tests: Fix a double-close of a GSource in tests

[Philip Withnall <pwithnall src gnome org>]

commit 7c714527080973781e45ed355369999444d4f695
Author: Philip Withnall <pwithnall endlessos org>
Date:   Mon May 16 14:11:13 2022 +0100

    tests: Fix a double-close of a GSource in tests
    
    This bug only gets triggered on BSD, because it calls `recv_message()`
    with `G_IO_HUP | G_IO_IN`. That takes two code paths in
    `recv_message()`, and ends up calling `shutdown_source()` twice. The
    second call causes a critical warning.
    
    Signed-off-by: Philip Withnall <pwithnall endlessos org>

 glib/tests/io-channel-basic.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)
---
diff --git a/glib/tests/io-channel-basic.c b/glib/tests/io-channel-basic.c
index 70b3a9dfca..b608a3cd45 100644
--- a/glib/tests/io-channel-basic.c
+++ b/glib/tests/io-channel-basic.c
@@ -96,8 +96,13 @@ read_all (int         fd,
 static void
 shutdown_source (gpointer data)
 {
-  if (g_source_remove (*(guint *) data))
+  guint *fd_ptr = data;
+
+  if (*fd_ptr != 0)
     {
+      g_source_remove (*fd_ptr);
+      *fd_ptr = 0;
+
       nrunning--;
       if (nrunning == 0)
         g_main_loop_quit (main_loop);