From 24bb100c6d50a451a8689bbf7d4347772427572a Mon Sep 17 00:00:00 2001
From: Edgar Asatryan <nstdio@gmail.com>
Date: Sat, 29 Jun 2019 16:42:17 +0400
Subject: [PATCH] Return empty unmodifiable set when no registered modules
 types.

---
 .../java/com/fasterxml/jackson/databind/ObjectMapper.java  | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/main/java/com/fasterxml/jackson/databind/ObjectMapper.java b/src/main/java/com/fasterxml/jackson/databind/ObjectMapper.java
index 16716be1a5..4e1ab83166 100644
--- a/src/main/java/com/fasterxml/jackson/databind/ObjectMapper.java
+++ b/src/main/java/com/fasterxml/jackson/databind/ObjectMapper.java
@@ -988,9 +988,10 @@ public ObjectMapper registerModules(Iterable<? extends Module> modules)
      *
      * @since 2.9.6
      */
-    public Set<Object> getRegisteredModuleIds()
-    {
-        return Collections.unmodifiableSet(_registeredModuleTypes);
+    public Set<Object> getRegisteredModuleIds() {
+        return _registeredModuleTypes == null ?
+                Collections.emptySet() :
+                Collections.unmodifiableSet(_registeredModuleTypes);
     }
 
     /**