master 8b98f87b92: Fix a crash when an X connection is dropped in some situations

[Po Lu]

branch: master
commit 8b98f87b924fcb2e79740063b36db1ed0b752853
Author: Po Lu <luangruo@yahoo.com>
Commit: Po Lu <luangruo@yahoo.com>

    Fix a crash when an X connection is dropped in some situations
    
    * src/xterm.c (x_flip_and_flush): Don't try to flush if
    `inhibit-redisplay' is t.
---
 src/xterm.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/xterm.c b/src/xterm.c
index f81d99ca12..c24de0f185 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -5618,6 +5618,12 @@ show_back_buffer (struct frame *f)
 static void
 x_flip_and_flush (struct frame *f)
 {
+  /* Flipping buffers requires a working connection to the X server,
+     which isn't always present if `inhibit-redisplay' is t, since
+     this can be called from the IO error handler.  */
+  if (!NILP (Vinhibit_redisplay))
+    return;
+
   block_input ();
 #ifdef HAVE_XDBE
   if (FRAME_X_NEED_BUFFER_FLIP (f))