Fix NPE and Bump Core Version (#453)

* Fix NPE when listener is null

* Bump core version and update changelog

CHANGELOG.md

@@ -2,7 +2,8 @@
 
 ## unreleased
 
-* Bump brinatree_android module dependency versions to `4.39.0`
+* Bump braintree_android module dependency versions to `4.40.1`
+* Fix NPE when `DropInListener` is null
 
 ## 6.13.0
 

Drop-In/src/main/java/com/braintreepayments/api/DropInClient.java

@@ -348,7 +348,7 @@ private void getPaymentMethodNonces(final FetchMostRecentPaymentMethodCallback c
     }
 
     void onDropInResult(DropInResult dropInResult) {
-        if (dropInResult != null) {
+        if (dropInResult != null && listener != null) {
             Exception error = dropInResult.getError();
             if (error != null) {
                 listener.onDropInFailure(error);

Drop-In/src/test/java/com/braintreepayments/api/DropInClientUnitTest.java

@@ -415,6 +415,16 @@ public void onDropInResult_whenResultIsNull_doesNothing() {
         verifyNoInteractions(listener);
     }
 
+    @Test
+    public void onDropInResult_whenListenerIsNull_doesNothing() {
+        DropInClientParams params = new DropInClientParams();
+        DropInClient sut = new DropInClient(params);
+
+
+        DropInResult dropInResult = new DropInResult();
+        sut.onDropInResult(dropInResult);
+    }
+
     @Test
     public void invalidateClientToken_forwardsInvocationIntoBraintreeClient() {
         BraintreeClient braintreeClient = new MockBraintreeClientBuilder().build();

build.gradle

@@ -7,7 +7,7 @@ buildscript {
         }
     }
 
-    ext.brainTreeVersion = "4.39.0"
+    ext.brainTreeVersion = "4.40.1"
 
     ext.deps = [
             "braintreeCore" : "com.braintreepayments.api:braintree-core:$brainTreeVersion",