message: [bugfix] Tab: line width can be zero
diff: @@ -256,7 +256,7 @@ export default create({
  }
  const tab = this.$refs.tabs[this.curActive];
  - const width = this.lineWidth || (tab.offsetWidth / 2);
  + const width = this.isDef(this.lineWidth) ? this.lineWidth : (tab.offsetWidth / 2);
  const left = tab.offsetLeft + (tab.offsetWidth - width) / 2;
  this.lineStyle = {
  