MarkdownConfig: Fix reference comparison with Boolean.TRUE

Change-Id: Ic950c5d224d6a79f9d44bc43f1f6285a4fc3b767
diff --git a/java/com/google/gitiles/doc/MarkdownConfig.java b/java/com/google/gitiles/doc/MarkdownConfig.java
index b4add94..4758654 100644
--- a/java/com/google/gitiles/doc/MarkdownConfig.java
+++ b/java/com/google/gitiles/doc/MarkdownConfig.java
@@ -78,7 +78,7 @@
     if (safeHtml) {
       f = cfg.getStringList("markdown", null, "allowiframe");
     }
-    allowAnyIFrame = f.length == 1 && StringUtils.toBooleanOrNull(f[0]) == Boolean.TRUE;
+    allowAnyIFrame = f.length == 1 && Boolean.TRUE.equals(StringUtils.toBooleanOrNull(f[0]));
     if (allowAnyIFrame) {
       allowIFrame = ImmutableList.of();
     } else {