Validator is undefined when child is inside a slot

Versions:

• VueJs: 2.3.3
• Vee-Validate: master (fc88f2a65d4424fb985f391817b36a125d9d33e4)

Description:

$validator is undefined when using inject: false for child components that are inside a <slot> container

Steps To Reproduce:

https://jsfiddle.net/Toilal/y46y3349/

[Toilal]

I have found the issue here : https://github.com/logaretm/vee-validate/blob/master/src/mixin.js#L7-L11

  mixin.provide = function providesValidator() {
    return {
      $validator: this.$validator
    };
  };

Problem is that when this.$validator is undefined, it actually inject in the component with an undefined value.

It should be fixed with the following

  mixin.provide = function providesValidator() {
    if (this.$validator) {
      return {
          $validator: this.$validator
      };
    }
  };

Then, it behaves like manually provided value (dummy in the JSFiddle) and VueJS traverse the tree component up until in finds a $validator instance. I just tested this change in my app and it fix my issue.

[Toilal]

It would be possible in the JSFiddle, but in my real app, items component comes from a dependency so I can’t add the injection code for it.

I think it should just traverse the component tree up until it finds a validator.