Avoid -fsanitize=enum

...when doing "Format - Page..." in Writer:

> cui/source/tabpages/tparea.cxx:268:12: runtime error: load of value 4294967295, which is not a valid value for type 'FillType'
>     #0 0x7f89ff653a41 in SvxAreaTabPage::Reset(SfxItemSet const*) cui/source/tabpages/tparea.cxx:268:12
>     #1 0x7f8d15524560 in SfxTabDialog::ActivatePageHdl(TabControl*) sfx2/source/dialog/tabdlg.cxx:1117:19
>     #2 0x7f8d1551b0e3 in SfxTabDialog::LinkStubActivatePageHdl(void*, TabControl*) sfx2/source/dialog/tabdlg.cxx:1035:1
>     #3 0x7f8cef623f37 in Link<TabControl*, void>::Call(TabControl*) const include/tools/link.hxx:84:45
>     #4 0x7f8cef5dfcaa in TabControl::ActivatePage() vcl/source/control/tabctrl.cxx:1601:19

Change-Id: I19dd3ed9d362132daa3f3be9fb0e9702a62bdeb0

cui/source/tabpages/tparea.cxx

@@ -270,7 +270,7 @@ void SvxAreaTabPage::Reset_Impl( const SfxItemSet* rAttrs )
 
 void SvxAreaTabPage::Reset( const SfxItemSet* rAttrs )
 {
-    FillType eFillType = static_cast<FillType>(maBox.GetCurrentButtonPos());
+    auto eFillType = maBox.GetCurrentButtonPos();
     switch(eFillType)
     {
         case SOLID: