fix(fcm): Gracefully handling non-json error responses (#508)

Author: hiranya911

src/main/java/com/google/firebase/messaging/FirebaseMessagingClientImpl.java

@@ -307,7 +307,7 @@ private MessagingServiceErrorResponse safeParse(String response) {
         try {
           return jsonFactory.createJsonParser(response)
               .parseAndClose(MessagingServiceErrorResponse.class);
-        } catch (IOException ignore) {
+        } catch (Exception ignore) {
           // Ignore any error that may occur while parsing the error response. The server
           // may have responded with a non-json payload.
         }

src/test/java/com/google/firebase/messaging/FirebaseMessagingClientImplTest.java

@@ -82,7 +82,7 @@ public class FirebaseMessagingClientImplTest {
       .setTopic("test-topic")
       .build();
   private static final List<Message> MESSAGE_LIST = ImmutableList.of(EMPTY_MESSAGE, EMPTY_MESSAGE);
-  
+
   private static final boolean DRY_RUN_ENABLED = true;
   private static final boolean DRY_RUN_DISABLED = false;
 
@@ -100,7 +100,7 @@ public void setUp() {
   @Test
   public void testSend() throws Exception {
     Map<Message, Map<String, Object>> testMessages = buildTestMessages();
-    
+
     for (Map.Entry<Message, Map<String, Object>> entry : testMessages.entrySet()) {
       response.setContent(MOCK_RESPONSE);
       String resp = client.send(entry.getKey(), DRY_RUN_DISABLED);
@@ -200,14 +200,14 @@ public void testSendErrorWithZeroContentResponse() {
   @Test
   public void testSendErrorWithMalformedResponse() {
     for (int code : HTTP_ERRORS) {
-      response.setStatusCode(code).setContent("not json");
+      response.setStatusCode(code).setContent("[not json]");
 
       try {
         client.send(EMPTY_MESSAGE, DRY_RUN_DISABLED);
         fail("No error thrown for HTTP error");
       } catch (FirebaseMessagingException error) {
         checkExceptionFromHttpResponse(error, HTTP_2_ERROR.get(code), null,
-            "Unexpected HTTP response with status: " + code + "\nnot json");
+            "Unexpected HTTP response with status: " + code + "\n[not json]");
       }
       checkRequestHeader(interceptor.getLastRequest());
     }