Do not initialize SimpleFunctionDescriptorImpl::userDataMap if it's empty

core/descriptors/src/org/jetbrains/kotlin/descriptors/impl/FunctionDescriptorImpl.java

@@ -824,6 +824,9 @@ public abstract class FunctionDescriptorImpl extends DeclarationDescriptorNonRoo
 
     // Don't use on published descriptors
     public <V> void putInUserDataMap(UserDataKey<V> key, Object value) {
+        if (userDataMap == null) {
+            userDataMap = new LinkedHashMap<UserDataKey<?>, Object>();
+        }
         userDataMap.put(key, value);
     }
 }

core/descriptors/src/org/jetbrains/kotlin/descriptors/impl/SimpleFunctionDescriptorImpl.java

@@ -79,7 +79,7 @@ public class SimpleFunctionDescriptorImpl extends FunctionDescriptorImpl impleme
         super.initialize(receiverParameterType, dispatchReceiverParameter, typeParameters, unsubstitutedValueParameters,
                          unsubstitutedReturnType, modality, visibility);
 
-        if (userData != null) {
+        if (userData != null && !userData.isEmpty()) {
             userDataMap = new LinkedHashMap<UserDataKey<?>, Object>(userData);
         }