[Bug 28754] New: In comdl32/tests/itemdlg.ok, update_layout() uses uninitialized window rect

http://bugs.winehq.org/show_bug.cgi?id=28754

Bug #: 28754
           Summary: In comdl32/tests/itemdlg.ok, update_layout() uses
                    uninitialized window rect
           Product: Wine
           Version: 1.3.30
          Platform: x86
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: comdlg32
        AssignedTo: [e-mail]
        ReportedBy: [e-mail]
    Classification: Unclassified

Running "make itemdlg.ok" in comdlg32/tests, valgrind complains

Conditional jump or move depends on uninitialised value(s)
   at update_layout (itemdlg.c:1114)
   by IFileDialog2_fnSetFileNameLabel (itemdlg.c:1968)
   by IFileOpenDialog_fnSetFileNameLabel (itemdlg.c:2231)
   by func_itemdlg (itemdlg.c:714)
   by run_test (test.h:556)
   by main (test.h:624)
 Uninitialised value was created by a stack allocation
   at update_layout (itemdlg.c:1098)

and a cascade of uninitialized values ensues that would be hard to
write a suppression for.  The uninitilialized value happens because
update_layout() calls GetClientRect on This->dlg_hwnd, which is NULL,
and doesn't check whether it succeeded.

The attached patch makes all the warnings go away, but I don't know if it's
the right thing to do.