Fix a problem with value define but not an Array

[lionel-bijaoui]

If the model is initialized with an empty string, when checked/clicked, the push was failing because value is not an array.

model: {
    checklist:''
},
schema: {
    fields: [
            {
            type: "checklist",
            label: "CHECKLIST",
            model: "checklist",
            listBox: true,
            values: [{
                name: "HTML5",
                value: "HTML5-123"
            }, {
                name: "Javascript",
                value: "Javascript-123"
            }],
            }
	]
}

TypeError: this.value.push is not a function

[icebob]

Mergeable

[lionel-bijaoui]

I found out that it doesn't really fix the problem. Another PR is coming.