Fix json filter call with 0 as a parameter (#2890)

Fix #2888

Author: posva

src/filters/index.js

@@ -19,7 +19,7 @@ export default {
     read: function (value, indent) {
       return typeof value === 'string'
         ? value
-        : JSON.stringify(value, null, Number(indent) || 2)
+        : JSON.stringify(value, null, arguments.length > 1 ? indent : 2)
     },
     write: function (value) {
       try {

test/unit/specs/filters/filters_spec.js

@@ -6,6 +6,7 @@ describe('Filters', function () {
     var obj = {a: {b: 2}}
     expect(filter(obj)).toBe(JSON.stringify(obj, null, 2))
     expect(filter(obj, 4)).toBe(JSON.stringify(obj, null, 4))
+    expect(filter(obj, 0)).toBe(JSON.stringify(obj, null, 0))
     // plain string
     expect(filter('1234')).toBe('1234')
   })