fix: the background image cannot be displayed when viewing the program

src/views/bigscreen/viewer/index.vue

@@ -62,7 +62,7 @@
     >
       <div
         class="c-viewer__background has-bg"
-        :style="backgroundStyle"
+        :style="backgroundStyles"
       />
       <widget
         v-for="(item, index) in widgets"