Fix issues with white theme & Forez join group screen

lib/forez/tour/join_group_pane.dart

@@ -44,6 +44,8 @@ class _JoinGroupPaneBody extends StatefulWidget {
 }
 
 class JoinGroupPaneBodyState extends State<_JoinGroupPaneBody> {
+  final _key = GlobalKey<AsyncScreenWidgetState>();
+
   List<Group> _groups;
   int _currChoice;
 
@@ -60,6 +62,7 @@ class JoinGroupPaneBodyState extends State<_JoinGroupPaneBody> {
 
   @override
   Widget build(BuildContext context) => AsyncScreenWidget(
+      key: _key,
       onReload: _load,
       onBuild: onBuild,
       errorMessage: tr("Failed to load the list of Forez groups!"));
@@ -107,7 +110,9 @@ class JoinGroupPaneBodyState extends State<_JoinGroupPaneBody> {
               _currGroup.registrationLevel != GroupRegistrationLevel.OPEN) ||
           _currGroup.membershipLevel == GroupMembershipLevel.PENDING) {
         await alert(context,
-            tr("You can not access this group yet, please wait for a member of the group to accept your request. Hopefully this will not be too long. Please check back soon!"));
+            tr("You can not access this group yet, please wait for a member of the group to accept your request.\nHopefully this will not be too long.\nPlease check back soon!"));
+
+        _key.currentState.refresh();
 
         return false;
       }
@@ -117,6 +122,7 @@ class JoinGroupPaneBodyState extends State<_JoinGroupPaneBody> {
     } catch (e, s) {
       logError(e, s);
       snack(context, tr("Failed to register to group!"));
+      _key.currentState.refresh();
       return false;
     }
   }

lib/ui/screens/group_access_denied_screen.dart

@@ -68,7 +68,10 @@ class _GroupAccessDeniedScreenState extends SafeState<GroupAccessDeniedScreen> {
               style: TextStyle(fontSize: 20),
             ),
             Spacer(),
-            Text(tr("A registration is required to access this group page.")),
+            Text(
+              tr("A registration is required to access this group page."),
+              textAlign: TextAlign.center,
+            ),
             Spacer(),
             GroupMembershipWidget(
               group: _group,

lib/ui/widgets/group_membership_widget.dart

@@ -140,6 +140,7 @@ class _GroupMembershipWidgetState extends SafeState<GroupMembershipWidget> {
     return RichText(
       text: TextSpan(
           text: tr("Request membership"),
+          style: blackForWhiteTheme(),
           recognizer: TapGestureRecognizer()
             ..onTap = () => _requestMembership()),
     );