Fix profile page when use system's font (#4774)

diff --git a/app/views/layouts/application.html.haml b/app/views/layouts/application.html.haml
index 0ba0ffc37e8f9c73aceeda357ce0c399f9bed9a2..e21fb1ce1452407ccd1ecab9f8f37a1ffc826640 100755 (executable)
--- a/app/views/layouts/application.html.haml
+++ b/app/views/layouts/application.html.haml
@@ -34,7 +34,7 @@
 
     = yield :header_tags
 
-  - body_classes ||= @body_classes
+  - body_classes ||= @body_classes || ''
   - body_classes += ' system-font' if current_account&.user&.setting_system_font_ui
 
   %body{ class: add_rtl_body_class(body_classes) }