Fix bug #14970 with crashes when deleting many frames on MS-Windows.

 src/w32fns.c (w32_wnd_proc) <WM_IME_STARTCOMPOSITION>: Make sure the
 frame which got the message is still alive, before dereferencing
 its pointer.
 src/frame.c (delete_frame): Test "this" frame's minibuffer window to
 be a live window, before using it as such.

1 files changed, 6 insertions, 3 deletions

diff --git a/src/frame.c b/src/frame.c
index 5fa54052cd2..0b59b43a445 100644
--- a/src/frame.c
+++ b/src/frame.c
@@ -1157,10 +1157,13 @@ delete_frame (Lisp_Object frame, Lisp_Object force)
 
       FOR_EACH_FRAME (frames, this)
         {
+          Lisp_Object fminiw;
+          struct frame *this_f;
+
           if (! EQ (this, frame)
-              && EQ (frame,
-                     WINDOW_FRAME (XWINDOW
-                                   (FRAME_MINIBUF_WINDOW (XFRAME (this))))))
+              && (this_f = XFRAME (this))
+              && WINDOWP (fminiw = FRAME_MINIBUF_WINDOW (this_f))
+              && EQ (frame, WINDOW_FRAME (XWINDOW (fminiw))))
             {
               /* If we MUST delete this frame, delete the other first.
                  But do this only if FORCE equals `noelisp'.  */