check argument of doCtags()

fixes ##4187

Author: vladak

opengrok-indexer/src/main/java/org/opengrok/indexer/analysis/AnalyzerGuru.java

@@ -18,7 +18,7 @@
  */
 
 /*
- * Copyright (c) 2005, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2005, 2023, Oracle and/or its affiliates. All rights reserved.
  * Portions Copyright (c) 2017, 2021, Chris Fraire <[email protected]>.
  */
 package org.opengrok.indexer.analysis;
@@ -57,6 +57,7 @@
 import org.apache.lucene.document.StringField;
 import org.apache.lucene.document.TextField;
 import org.apache.lucene.util.BytesRef;
+import org.jetbrains.annotations.Nullable;
 import org.opengrok.indexer.analysis.FileAnalyzerFactory.Matcher;
 import org.opengrok.indexer.analysis.ada.AdaAnalyzerFactory;
 import org.opengrok.indexer.analysis.archive.BZip2AnalyzerFactory;
@@ -663,7 +664,7 @@ private static void populateDocumentHistory(Document doc, File file) {
      * @throws java.io.IOException If an error occurs while creating the output
      */
     public static void writeXref(AnalyzerFactory factory, Reader in,
-            Writer out, Definitions defs,
+            Writer out, @Nullable Definitions defs,
             Annotation annotation, Project project, File file)
             throws IOException {
 
@@ -704,7 +705,7 @@ public static void writeXref(AnalyzerFactory factory, Reader in,
      */
     public static void writeDumpedXref(String contextPath,
             AnalyzerFactory factory, Reader in, Writer out,
-            Definitions defs, Annotation annotation, Project project, File file) throws IOException {
+            @Nullable Definitions defs, Annotation annotation, Project project, File file) throws IOException {
 
         File xrefTemp = File.createTempFile("ogxref", ".html");
         try {

opengrok-web/src/main/webapp/xref.jspf

@@ -63,6 +63,8 @@ org.opengrok.indexer.web.QueryParameters"
                 if (HistoryGuru.getInstance().getRevision(tempf, resourceFile.getParent(), basename, rev)) {
                     in = new BufferedInputStream(new FileInputStream(tempf));
                 } else {
+                    LOGGER.log(Level.WARNING, "failed to retrieve history contents of ''{0}'' in revision {1}",
+                            new Object[]{resourceFile, rev});
                     tempf.delete();
                     tempf = null;
                 }
@@ -96,7 +98,7 @@ org.opengrok.indexer.web.QueryParameters"
                         Definitions defs = null;
                         ObjectPool<Ctags> ctagsPool = cfg.getEnv().getIndexerParallelizer().getCtagsPool();
                         int tries = 2;
-                        while (cfg.getEnv().isWebappCtags()) {
+                        while (cfg.getEnv().isWebappCtags() && tempf != null) {
                             Ctags ctags = ctagsPool.get();
                             try {
                                 ctags.setTabSize(project != null ?