Ensure we don't crash when checking for cancelling print job

Don't dereference sm_abortWindow without checking that it is non-null in
wxAbortProc(): even though it's not supposed to happen, it still somehow
does, apparently, so just log a debug message instead of crashing in
this case.

See wxWidgets#23927.

(cherry picked from commit 9a72819)

Author: vadz

docs/changes.txt

@@ -324,6 +324,7 @@ wxMSW:
 - Fix wrong wxWindowsPrintNativeData initialization (Stefan Ziegler, #23685).
 - Fix position of wxStaticBox label after DPI change (Maarten Bent, #23740).
 - Fix background colour of empty cells in wxDataViewCtrl (#23708).
+- Fix possible (even if rare) crash in printer progress dialog (#23927).
 
 wxOSX:
 

src/msw/printwin.cpp

@@ -425,12 +425,24 @@ BOOL CALLBACK wxAbortProc(HDC WXUNUSED(hdc), int WXUNUSED(error))
         return(TRUE);
 
     /* Process messages intended for the abort dialog box */
+    const HWND hwnd = GetHwndOf(wxPrinterBase::sm_abortWindow);
 
     while (!wxPrinterBase::sm_abortIt && ::PeekMessage(&msg, 0, 0, 0, TRUE))
-        if (!IsDialogMessage((HWND) wxPrinterBase::sm_abortWindow->GetHWND(), &msg)) {
+    {
+        // Apparently handling the message may, somehow, result in
+        // sm_abortWindow being destroyed, so guard against this happening.
+        if (!wxPrinterBase::sm_abortWindow)
+        {
+            wxLogDebug(wxS("Print abort dialog unexpected disappeared."));
+            return TRUE;
+        }
+
+        if (!IsDialogMessage(hwnd, &msg))
+        {
             TranslateMessage(&msg);
             DispatchMessage(&msg);
         }
+    }
 
     /* bAbort is TRUE (return is FALSE) if the user has aborted */