fix: close #64 , color-picker transfer

Author: likuner

examples/routers/color-picker.vue

@@ -1,7 +1,7 @@
 <template>
     <Row>
         <Col span="8">
-            <ColorPicker v-model="color6" size="large" />
+            <ColorPicker v-model="color6" size="large" transfer/>
         </Col>
         <Col span="8">
             <ColorPicker v-model="color6" />

src/components/color-picker/color-picker.vue

@@ -418,7 +418,7 @@
                     }
 
                     if (this.transfer) {
-                        const { $el } = this.$refs.drop;
+                        const $el = this.$refs.drop.$refs.drop;
                         if ($el === event.target || $el.contains(event.target)) {
                             return;
                         }