fixed transex3 out of bounds access to vMergeEntryVector

transex3 crashed if a new language was added to the StringArray
PairedList in svtools/source/misc/langtab.src and that resource was
attempted to be built.

For the new entry doesn't exist a MergeEntrys entry in vMergeEntryVector
yet, but ExportList::GetSourceLanguageListEntryCount() already includes
it so nMaxList is greater than size of vMergeEntryVector. Check nLIndex
first.

Change-Id: I3b706bea7aea7cd7ecd8245d99587b944510952d

l10ntools/source/export.cxx

@@ -1476,7 +1476,7 @@ void Export::MergeRest( ResData *pResData, sal_uInt16 nMode )
                                 }
                             }
 
-                            if( bTranslateList )
+                            if( bTranslateList && nLIndex < vMergeEntryVector.size() )
                             {
                                 OString sText;
                                 sal_Bool bText;