show a message if the sd card is unmounted

lua/main_menu.lua

@@ -90,6 +90,7 @@ return widgets.MenuScreen:new {
     -- a list of all available database indexes, but could also be the contents
     -- of the SD card root.
 
+    if require("sd_card").mounted:get() then
       local list = lvgl.List(self.root, {
         w = lvgl.PCT(100),
         h = lvgl.PCT(100),
@@ -111,6 +112,20 @@ return widgets.MenuScreen:new {
           btn:focus()
         end
       end
+    else
+      local container = self.root:Object {
+        w = lvgl.PCT(100),
+        flex_grow = 1,
+      }
+      container:Label {
+        w = lvgl.PCT(100),
+        h = lvgl.SIZE_CONTENT,
+        text_align = 2,
+        long_mode = 0,
+        margin_all = 4,
+        text = "SD Card is not inserted or could not be opened.",
+      }:center();
+    end
 
     -- Finally, the bottom bar with icon buttons for other device features.
 

src/tangara/system_fsm/running.cpp

@@ -75,6 +75,7 @@ void Running::react(const SdDetectChanged& ev) {
   }
 
   if (ev.has_sd_card && !sStorage) {
+    vTaskDelay(pdMS_TO_TICKS(500));
     mountStorage();
   }
 

src/tangara/ui/lvgl_task.cpp

@@ -55,7 +55,8 @@ auto UiTask::Main() -> void {
       current_screen_ = screen;
     }
 
-    if (input_ && current_screen_->group() != current_group) {
+    if (input_ && current_screen_ &&
+        current_screen_->group() != current_group) {
       current_group = current_screen_->group();
       input_->setGroup(current_group);
     }