directly get matching a11y if it exists

rather than check if it exists, and then get it if it exists

I wonder if the else branch from...

commit 0c2229dc
Date:   Fri Mar 24 13:04:32 2017 +0100

    tdf#58624 sw: fix ~SwAccessibleContext() use-after-free race

is still relevant after this

Change-Id: Idabea01f0c450b07b75214c5a83460e1d0319802
Reviewed-on: https://gerrit.libreoffice.org/54904Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

sw/source/core/access/acccontext.cxx

@@ -401,13 +401,8 @@ void SwAccessibleContext::DisposeChildren(const SwFrame *pFrame,
         const SwFrame* pLower = rLower.GetSwFrame();
         if( pLower )
         {
-            ::rtl::Reference< SwAccessibleContext > xAccImpl;
-            if (rLower.IsAccessible(GetShell()->IsPreview())
-                       // tdf#117601 dispose the darn thing if it ever was accessible
-                    || GetMap()->Contains(pLower))
-            {
-                xAccImpl = GetMap()->GetContextImpl( pLower, false );
-            }
+            // tdf#117601 dispose the darn thing if it ever was accessible
+            ::rtl::Reference<SwAccessibleContext> xAccImpl = GetMap()->GetContextImpl(pLower, false);
             if( xAccImpl.is() )
                 xAccImpl->Dispose( bRecursive );
             else