add packages for flutter secure storage

.gitlab-ci.yml

@@ -18,7 +18,7 @@ linux_build:
   stage: build
   script:
     - apt-get update
-    - apt-get install -y --no-install-recommends cmake ninja-build clang build-essential pkg-config libgtk-3-dev liblzma-dev lcov libvlc-dev vlc
+    - apt-get install -y --no-install-recommends cmake ninja-build clang build-essential pkg-config libgtk-3-dev liblzma-dev lcov libvlc-dev vlc libsecret-1-dev libjsoncpp-dev
     - flutter config --enable-linux-desktop
     - flutter packages get
     - flutter build linux

lib/screen_loading.dart

@@ -5,7 +5,10 @@ class ScreenLoading extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    return Column(children: const <Widget>[
+    return Column(
+        mainAxisAlignment: MainAxisAlignment.center,
+        crossAxisAlignment: CrossAxisAlignment.center,
+        children: const <Widget>[
           SizedBox(
             width: 60,
             height: 60,