use parantheses to prevent wrong evaluation

Change-Id: Ia872b5648286fd76039f7c397ea78e18bc2ad6b8

sc/source/core/data/document.cxx

@@ -4213,7 +4213,7 @@ void ScDocument::ApplyPatternIfNumberformatIncompatible( const ScRange& rRange,
 
 void ScDocument::AddCondFormatData( const ScRangeList& rRange, SCTAB nTab, sal_uInt32 nIndex )
 {
-    if(!static_cast<SCTAB>(nTab) < maTabs.size())
+    if(!(static_cast<size_t>(nTab) < maTabs.size()))
         return;
 
     if(!maTabs[nTab])