Do not insert newlines when converting empty arrays to json string and JSON_C_TO_STRING_PRETTY is used

[simplepad]

Describe the bug
When json-c converts a json array to a json string and the flag JSON_C_TO_STRING_PRETTY is used, it inserts a newline even if the array is empty.

json-c/json_object.c

Lines 1377 to 1378 in d28ac67

	if (flags & JSON_C_TO_STRING_PRETTY)
	printbuf_strappend(pb, "\n");

Here in the if condition it should check if the array is not empty, otherwise it looks like this:

{
  "mystring": "hello",
  "my_empty_array": [
  ]
}

I think it would be better if it looked like this:

{
  "mystring": "hello",
  "my_empty_array": []
}

Pretty insignificant, I know 😄

Steps To Reproduce

struct json_object * object = json_object_new_object();
json_object_object_add(object, "my_empty_array", json_object_new_array());
puts(json_object_to_json_string_ext(object, JSON_C_TO_STRING_PRETTY | JSON_C_TO_STRING_SPACED));

Version and Platform

• json-c version: json-c-0.16
• OS: Arch Linux
• Custom cmake/build flags, if any: none

[hhj1988]

yum -y install gcc-c++

[hawicz]

Sounds like a good idea. 👍