Fix offline issues in Projects page with no/expired token (#3326)

1. incorrect "no workspace detected" message
2. endless busy wait on the home tab (unable to switch projects)
3. endless loop of requesting projects in the second tab

app/qml/project/MMProjectController.qml

@@ -303,7 +303,7 @@ Item {
               if ( !__merginApi.apiSupportsWorkspaces ) {
                 return false;
               }
-              if ( !__merginApi.userAuth.hasAuthData() ) {
+              if ( !__merginApi.userAuth.hasValidToken() ) {
                 return false;
               }
               // do not show the banner in case of accepting invitation or creating a workspace
@@ -623,6 +623,10 @@ Item {
       stackView.pending = false
     }
 
+    function onListProjectsFailed() {
+      stackView.pending = false
+    }
+
     function onApiVersionStatusChanged() {
       stackView.pending = false
 
@@ -642,7 +646,7 @@ Item {
     function onAuthChanged() {
       stackView.pending = false
 
-      if ( __merginApi.userAuth.hasAuthData() ) {
+      if ( __merginApi.userAuth.hasValidToken() ) {
 
         if ( __merginApi.serverType === MM.MerginServerType.OLD || ( stackView.currentItem.objectName === "loginPage" ) ) {
           stackView.popPage( "loginPage" )

core/merginuserauth.h

@@ -36,7 +36,7 @@ class MerginUserAuth: public QObject
 
     //! Returns true if we have a token and it is not expired,
     //! i.e. we should be good to do authenticated requests.
-    bool hasValidToken() const;
+    Q_INVOKABLE bool hasValidToken() const;
 
     void clear();