address review comment

Author: vladak

opengrok-web/src/main/webapp/history.jsp

@@ -47,6 +47,7 @@ org.opengrok.indexer.web.Util"
 %>
 <%@ page import="jakarta.servlet.http.HttpServletResponse" %>
 <%@ page import="org.opengrok.indexer.web.SortOrder" %>
+<%@ page import="java.util.Optional" %>
 <%/* ---------------------- history.jsp start --------------------- */
 {
     final Logger LOGGER = LoggerFactory.getLogger(getClass());
@@ -257,17 +258,15 @@ document.domReady.push(function() {domReadyHistory();});
             <%
             int count=0;
             for (HistoryEntry entry : hist.getHistoryEntries(maxItems, startIndex)) {
-                String dispRev = entry.getDisplayRevision();
-                if (dispRev == null || dispRev.isEmpty()) {
-                    dispRev = "";
-                }
-                dispRev = Util.htmlize(dispRev);
-                String rev = entry.getRevision();
-                if (rev == null || rev.isEmpty()) {
-                    rev = "";
-                }
-                String tags = hist.getTags().get(rev);
+                final String dispRev = Optional.ofNullable(entry).
+                        map(HistoryEntry::getDisplayRevision).
+                        map(Util::htmlize).
+                        orElse("");
+                final String rev = Optional.ofNullable(entry).
+                        map(HistoryEntry::getRevision).
+                        orElse("");
 
+                String tags = hist.getTags().get(rev);
                 if (tags != null) {
                     int colspan;
                     if (cfg.isDir())