speed up emoji picker somewhat

src/components/emoji_picker/emoji_picker.js

@@ -150,7 +150,9 @@ const EmojiPicker = {
     },
     showPicker () {
       this.$refs.popover.showPopover()
-      this.onShowing()
+      this.$nextTick(() => {
+        this.onShowing()
+      })
     },
     hidePicker () {
       this.$refs.popover.hidePopover()

src/components/emoji_picker/emoji_picker.vue

@@ -89,6 +89,7 @@
             class="emoji-groups"
             :class="groupsScrolledClass"
             :min-item-size="minItemSize"
+            :buffer="minItemSize"
             :items="emojiItems"
             :emit-update="true"
             @update="onScroll"

src/modules/instance.js

@@ -374,6 +374,8 @@ const instance = {
             // should have been "pack" field, that would be more useful
           }).sort(byPackThenByName)
           commit('setInstanceOption', { name: 'customEmoji', value: emoji })
+          state.standardEmojiGroupList = null
+          state.standardEmojiList = null
         } else {
           throw (res)
         }