fix readme

README.md

@@ -34,7 +34,7 @@ export default {
 - an "object" with the following attributes:
   - `mask`: same as above
   - `unmaskedVar`: name of a variable defined in the "data" section of the component that will receive the "unmasked" text. It may be a structure (eg`"a.bc.d"`), but the first "level" must exists
-  - `nullIfEmpty`: Set `"unmaskedVar"` to null if the input value is empty. Default to **true**  
+  - `nullIfEmpty`: Set `"unmaskedVar"` to null if the input value is empty. Defaults to **true**  
   - `tokens`: An array of token objects that will replace the default ones. eg `tokens="[{ 'Y': {pattern: /[0-9]/ }]"`
 
 ### Tokens (From vue-the-mask)