fix eslint warnings

src/components/checkbox/checkbox.vue

@@ -12,8 +12,8 @@
     >
     <i class="checkbox-indicator" />
     <span
-      class="label"
       v-if="!!$slots.default"
+      class="label"
     >
       <slot />
     </span>

src/components/tab_switcher/tab_switcher.js

@@ -12,11 +12,13 @@ export default Vue.component('tab-switcher', {
     },
     onSwitch: {
       required: false,
-      type: Function
+      type: Function,
+      default: undefined
     },
     activeTab: {
       required: false,
-      type: String
+      type: String,
+      default: undefined
     },
     scrollableTabs: {
       required: false,