fix: Support create empty shared link

src/intTest/java/com/box/sdk/BoxFileIT.java

@@ -943,6 +943,21 @@ public void setsVanityNameOnASharedLink() {
         }
     }
 
+    @Test
+    public void createDefaultSharedLink() {
+        BoxAPIConnection api = jwtApiForServiceAccount();
+        BoxFile uploadedFile = null;
+        try {
+            uploadedFile = uploadFileToUniqueFolderWithSomeContent(api, "file_to_share.txt");
+            BoxSharedLinkRequest request = new BoxSharedLinkRequest();
+            uploadedFile.createSharedLink(request);
+            BoxSharedLink sharedLink = uploadedFile.getInfo().getSharedLink();
+            assertThat(sharedLink, is(notNullValue()));
+        } finally {
+            deleteFile(uploadedFile);
+        }
+    }
+
     @Test
     public void setsAndRetrievesDispositionAt() throws ParseException {
         BoxAPIConnection api = jwtApiForServiceAccount();

src/main/java/com/box/sdk/BoxJSONObject.java

@@ -213,7 +213,7 @@ void update(JsonObject jsonObject) {
      *
      * @return a JsonObject containing the pending changes.
      */
-    private JsonObject getPendingJSONObject() {
+    protected JsonObject getPendingJSONObject() {
         for (Map.Entry<String, BoxJSONObject> entry : this.children.entrySet()) {
             BoxJSONObject child = entry.getValue();
             JsonObject jsonObject = child.getPendingJSONObject();

src/main/java/com/box/sdk/BoxSharedLink.java

@@ -231,6 +231,15 @@ private Access parseAccessValue(JsonValue value) {
         return Access.valueOf(accessString);
     }
 
+    @Override
+    protected JsonObject getPendingJSONObject() {
+        JsonObject result = super.getPendingJSONObject();
+        if (result == null) {
+            result = new JsonObject();
+        }
+        return result;
+    }
+
     @Override
     void parseJSONMember(JsonObject.Member member) {
         JsonValue value = member.getValue();

src/test/java/com/box/sdk/BoxFileTest.java

@@ -1033,6 +1033,30 @@ public String getJSON() {
         file.createSharedLink(sharedLink);
     }
 
+    @Test
+    public void createDefaultSharedLink() {
+        //given
+        BoxAPIConnection api = new BoxAPIConnectionForTests("");
+        api.setRequestInterceptor(
+            request -> {
+                //then
+                String requestString = request.bodyToString();
+                assertThat(requestString, is("{\"shared_link\":{}}"));
+                return new BoxJSONResponse() {
+                    @Override
+                    public String getJSON() {
+                        return "{}";
+                    }
+                };
+            }
+        );
+        BoxSharedLinkRequest sharedLink = new BoxSharedLinkRequest();
+
+        //when
+        BoxFile file = new BoxFile(api, "12345");
+        file.createSharedLink(sharedLink);
+    }
+
     @Test
     public void setMetadataWorksWhenNoChangesSubmittedAndConflictOccured() {
         // given