[Bug Report] v-item-group/v-item incorrectly tracks active v-item

[UglyHobbitFeet]

Versions and Environment

Vuetify: 1.3.15
Vue: 2.5.21
Browsers: Firefox 64.0, Google Chrome
OS: Windows 7, Linux

Steps to reproduce

Click the plus icon until you have three tabs. The last tab should be shown as active.
Click the minus icon. The first tab should be active. Instead the last tab is incorrectly being shown as active

Expected Behavior

Click the minus icon. The first tab should be active.

Actual Behavior

Click the minus icon. The last tab is incorrectly being shown as active

Reproduction Link

https://codepen.io/uglyhobbitfeet/pen/xmPjqM?editors=1111

[johnleider]

Fixed in f22d754