fix(Badge/Button): support numeric zero as visible label (#4116)

Author: malik-jouda

src/runtime/components/elements/Badge.vue

@@ -5,7 +5,7 @@
     </slot>
 
     <slot>
-      <span v-if="label">
+      <span v-if="label !== undefined && label !== null">
         {{ label }}
       </span>
     </slot>

src/runtime/components/elements/Button.vue

@@ -5,7 +5,7 @@
     </slot>
 
     <slot>
-      <span v-if="label" :class="[truncate ? ui.truncate : '']">
+      <span v-if="label !== undefined && label !== null" :class="[truncate ? ui.truncate : '']">
         {{ label }}
       </span>
     </slot>