Avoid IllegalArgumentException, and log condition

Accommodate a repository that can transiently
return errors, such as Perforce when a login
expires.

Author: idodeclare

opengrok-indexer/src/main/java/org/opengrok/indexer/search/context/HistoryContext.java

@@ -108,6 +108,10 @@ public boolean getContext(File src, String path, Writer out, String context) thr
             return false;
         }
         History hist = HistoryGuru.getInstance().getHistory(src);
+        if (hist == null) {
+            LOGGER.log(Level.INFO, "Null history got for {0}", src);
+            return false;
+        }
         return getHistoryContext(hist, path, out, null, context);
     }