Avoid unnecessary operations on an OUString

Change-Id: I1820711664a6aa18587e1e4a3d74a8e4cbfcc07e
Reviewed-on: https://gerrit.libreoffice.org/1537Reviewed-by: Luboš Luňák <l.lunak@suse.cz>
Tested-by: Luboš Luňák <l.lunak@suse.cz>

sd/source/ui/annotations/annotationmanager.cxx

@@ -160,11 +160,11 @@ OUString getAnnotationDateTimeString( const Reference< XAnnotation >& xAnnotatio
         Date aSysDate( Date::SYSTEM );
         Date aDate = Date( aDateTime.Day, aDateTime.Month, aDateTime.Year );
         if (aDate==aSysDate)
-            sRet = sRet + String(SdResId(STR_ANNOTATION_TODAY));
+            sRet = SdResId(STR_ANNOTATION_TODAY);
         else if (aDate == Date(aSysDate-1))
-            sRet = sRet + String(SdResId(STR_ANNOTATION_YESTERDAY));
+            sRet = SdResId(STR_ANNOTATION_YESTERDAY);
         else if (aDate.IsValidAndGregorian() )
-            sRet = sRet + rLocalData.getDate(aDate);
+            sRet = rLocalData.getDate(aDate);
 
         Time aTime( aDateTime.Hours, aDateTime.Minutes, aDateTime.Seconds, aDateTime.HundredthSeconds );
         if(aTime.GetTime() != 0)