If the downloadable themes cache dir doesn't exist, force redownload.

This should fix an issue with the Theme Chooser sometimes showing
only locally installed themes by default forcing the user to manually
refresh the downloadable themes list via the popup menu.  If the
downloadable themes cache dir does not exist, we trigger a download
attempt automatically when entering the Theme Chooser.

mythtv/programs/mythfrontend/themechooser.cpp

@@ -195,6 +195,8 @@ void ThemeChooser::Load(void)
     QString themeSite = QString("%1/%2")
         .arg(gCoreContext->GetSetting("ThemeRepositoryURL",
              "http://themes.mythtv.org/themes/repository")).arg(MythVersion);
+    QDir remoteThemesDir(GetMythUI()->GetThemeCacheDir()
+                             .append("/themechooser/").append(MythVersion));
 
     int downloadFailures =
         gCoreContext->GetNumSetting("ThemeInfoDownloadFailures", 0);
@@ -208,6 +210,9 @@ void ThemeChooser::Load(void)
                         "remote theme list download").arg(remoteThemesFile));
             m_refreshDownloadableThemes = true;
         }
+
+        if (!remoteThemesDir.exists())
+            m_refreshDownloadableThemes = true;
     }
     else if (downloadFailures < 2) // (and themes.zip does not exist)
     {
@@ -243,9 +248,6 @@ void ThemeChooser::Load(void)
         }
     }
 
-    QDir remoteThemesDir(GetMythUI()->GetThemeCacheDir()
-                             .append("/themechooser/").append(MythVersion));
-
     if ((QFile::exists(remoteThemesFile)) &&
         (remoteThemesDir.exists()))
     {