Show home page if opening book fails

src/calibre/gui2/viewer/ui.py

@@ -261,6 +261,7 @@ class EbookViewer(MainWindow):
             error_dialog(self, _('Loading book failed'), _(
                 'Failed to open the book at {0}. Click "Show details" for more info.').format(data['pathtoebook']),
                 det_msg=data['tb'], show=True)
+            self.web_view.show_home_page()
             return
         set_book_path(data['base'], data['pathtoebook'])
         self.current_book_data = data

src/calibre/gui2/viewer/web_view.py

@@ -211,6 +211,7 @@ class ViewerBridge(Bridge):
     goto_cfi = to_js()
     full_screen_state_changed = to_js()
     get_current_cfi = to_js()
+    show_home_page = to_js()
 
 
 def apply_font_settings(page_or_view):
@@ -470,3 +471,6 @@ class WebView(RestartingWebEngineView):
 
     def get_current_cfi(self, callback):
         self.do_callback('get_current_cfi', callback)
+
+    def show_home_page(self):
+        self.execute_when_ready('show_home_page')

src/pyj/viewer-main.pyj

@@ -198,6 +198,11 @@ def create_view(prefs, all_font_families, field_metadata):
         view.overlay.open_book(False)
 
 
+@from_python
+def show_home_page():
+    view.overlay.open_book(False)
+
+
 @from_python
 def show_preparing_message(msg):
     view.show_loading_message(msg)