Resolves: tdf#93113 crash on revisiting insert special character

this effectively reverts

commit c43ee00e
Author: Herbert Duerr <hdu@openoffice.org>
Date:   Wed Aug 15 13:20:51 2001 +0000

    #91025# reduce flicker in charmap dialog

in favour of the new double buffering

Paint is calling RecalculateFont which calls SelectIndex
which calls Update which calls Paint, boom

Change-Id: I69e9f53b7db09837ff08a2ce9fc6f81a52b5c794
(cherry picked from commit 79395c93)
Reviewed-on: https://gerrit.libreoffice.org/17674Reviewed-by: Adolfo Jayme Barrientos <fitojb@ubuntu.com>
Tested-by: Adolfo Jayme Barrientos <fitojb@ubuntu.com>

svx/source/dialog/charmap.cxx

@@ -602,7 +602,6 @@ void SvxShowCharSet::SelectIndex( int nNewIndex, bool bFocus )
         aVscrollSB->SetThumbPos( nNewPos );
         nSelectedIndex = bFocus ? nMapIndex+1 : -1;
         Invalidate();
-        Update();
     }
     else if( nNewIndex < FirstInView() )
     {
@@ -612,8 +611,6 @@ void SvxShowCharSet::SelectIndex( int nNewIndex, bool bFocus )
         aVscrollSB->SetThumbPos( nOldPos - nDelta );
         nSelectedIndex = nNewIndex;
         Invalidate();
-        if( nDelta )
-            Update();
     }
     else if( nNewIndex > LastInView() )
     {
@@ -626,10 +623,9 @@ void SvxShowCharSet::SelectIndex( int nNewIndex, bool bFocus )
             nSelectedIndex = nNewIndex;
             Invalidate();
         }
-        if( nOldPos != aVscrollSB->GetThumbPos() )
+        else if (nOldPos != aVscrollSB->GetThumbPos())
         {
             Invalidate();
-            Update();
         }
     }
     else