SEPA Launcher API [Tests]

SEPADirectDebit/src/main/java/com/braintreepayments/api/SEPADirectDebitClient.java

@@ -128,6 +128,7 @@ public void onBrowserSwitchResult(@NonNull SEPADirectDebitBrowserSwitchResult se
 
         if (browserSwitchResult == null) {
             callback.onResult(null, new BraintreeException("An unexpected error occurred."));
+            return;
         }
 
         int result = browserSwitchResult.getStatus();

SEPADirectDebit/src/main/java/com/braintreepayments/api/SEPADirectDebitFlowStartedCallback.java

@@ -16,5 +16,5 @@ public interface SEPADirectDebitFlowStartedCallback {
      *                                {@link SEPADirectDebitLauncher#launch(FragmentActivity, SEPADirectDebitResponse)}
      * @param error                   an exception that occurred while initiating the SEPA transaction
      */
-    void onResult(SEPADirectDebitResponse sepaDirectDebitResponse, @Nullable Exception error);
+    void onResult(@Nullable SEPADirectDebitResponse sepaDirectDebitResponse, @Nullable Exception error);
 }

SEPADirectDebit/src/main/java/com/braintreepayments/api/SEPADirectDebitResponse.java

@@ -1,5 +1,6 @@
 package com.braintreepayments.api;
 
+import androidx.annotation.Nullable;
 import androidx.fragment.app.FragmentActivity;
 
 /**
@@ -31,7 +32,7 @@ BrowserSwitchOptions getBrowserSwitchOptions() {
      *
      * @return {@link SEPADirectDebitNonce}
      */
-    public SEPADirectDebitNonce getNonce() {
+    public @Nullable SEPADirectDebitNonce getNonce() {
         return this.sepaDirectDebitNonce;
     }
 }