Don't show video overlay when no video is present

Test: Manual
Change-Id: Ib88cd8a6d8d0d89b32e20dd7e151166287628d53

tools/winscope/src/App.vue

@@ -95,6 +95,8 @@ export default {
       this.files.forEach(function(item) { item.destroy(); })
       this.files = [];
       this.activeDataView = null;
+      this.activeFile = null;
+      this.video = null;
     },
     onDataViewFocus(file) {
       this.activeFile = file;

tools/winscope/src/BottomNavigation.vue

@@ -20,6 +20,7 @@
         class="video-overlay"
         v-show="minimized && showVideoOverlay"
         position="bottomLeft"
+        v-if="video"
       >
         <template slot="header">
           <div class="close-video-overlay" @click="closeVideoOverlay">

tools/winscope/yarn.lock

@@ -2295,11 +2295,16 @@ ee-first@1.1.1:
   resolved "https://registry.yarnpkg.com/ee-first/-/ee-first-1.1.1.tgz#590c61156b0ae2f4f0255732a158b266bc56b21d"
   integrity sha1-WQxhFWsK4vTwJVcyoViyZrxWsh0=
 
-electron-to-chromium@^1.2.7, electron-to-chromium@^1.3.47:
+electron-to-chromium@^1.2.7:
   version "1.3.458"
   resolved "https://registry.yarnpkg.com/electron-to-chromium/-/electron-to-chromium-1.3.458.tgz#4ef179f9a0f1d8a658180c09b21bf73edddfc5eb"
   integrity sha512-OjRkb0igW0oKE2QbzS7vBYrm7xjW/KRTtIj0OGGx57jr/YhBiKb7oZvdbaojqjfCb/7LbnwsbMbdsYjthdJbAw==
 
+electron-to-chromium@^1.3.413:
+  version "1.3.462"
+  resolved "https://registry.yarnpkg.com/electron-to-chromium/-/electron-to-chromium-1.3.462.tgz#82087404c20ed664963ececab23337ac7a150e21"
+  integrity sha512-HST/xWLOeA0LGUhxBqvcPDDUGHjB6rn99VBgPWmaHv+zqwXgOaZO5RnRcd5owjRE7nh+z1c0SwcK8qP8o7sofg==
+
 elliptic@^6.0.0, elliptic@^6.5.2:
   version "6.5.2"
   resolved "https://registry.yarnpkg.com/elliptic/-/elliptic-6.5.2.tgz#05c5678d7173c049d8ca433552224a495d0e3762"