fix isValueEmpty bug when working with integers

src/components/Select.vue

@@ -1082,7 +1082,7 @@
           if (typeof this.mutableValue === 'object') {
             return ! Object.keys(this.mutableValue).length
           }
-          return !this.mutableValue.length
+          return ! this.valueAsArray.length
         }
 
         return true;

test/unit/specs/Select.spec.js

@@ -249,6 +249,19 @@ describe('Select.vue', () => {
 			expect(vm.$children[0].isOptionSelected('foo')).toEqual(true)
 		}),
 
+		it('can work with an array of integers', () => {
+			const vm = new Vue({
+				template: '<div><v-select :options="[1,2,3,4,5]" v-model="value"></v-select></div>',
+				components: {vSelect},
+				data: {
+					value: 5,
+				}
+			}).$mount()
+
+			expect(vm.$children[0].isOptionSelected(5)).toEqual(true)
+			expect(vm.$children[0].isValueEmpty).toEqual(false)
+		})
+
     describe('change Event', () => {
 			it('will trigger the input event when the selection changes', (done) => {
 				const vm = new Vue({