add warn when enable stealth mode & add nav valid check (#1823)

* add warn when enable stealth

* change FLASH ERROR to FLASH ERR cuz previous one were overlapped with date

* check if nav is valid

firmware/application/ui_navigation.cpp

@@ -315,8 +315,15 @@ SystemStatusView::SystemStatusView(
         refresh();
     };
 
-    toggle_stealth.on_change = [this](bool v) {
+    toggle_stealth.on_change = [this, &nav](bool v) {
         pmem::set_stealth_mode(v);
+        if (nav.is_valid() && v) {
+            nav.display_modal(
+                "Stealth",
+                "You just enabled stealth mode.\n"
+                "When you transmit,\n"
+                "screen will turn off;\n");
+        }
         refresh();
     };
 
@@ -553,7 +560,7 @@ InformationView::InformationView(
 #endif
 
     if (firmware_checksum_error()) {
-        version.set("FLASH ERROR");
+        version.set("FLASH ERR");
         version.set_style(&Styles::red);
     }
 
@@ -585,6 +592,10 @@ bool NavigationView::is_top() const {
     return view_stack.size() == 1;
 }
 
+bool NavigationView::is_valid() const {
+    return view_stack.size() != 0;  // work around to check if nav is valid, not elegant i know. so TODO
+}
+
 View* NavigationView::push_view(std::unique_ptr<View> new_view) {
     free_view();
 

firmware/application/ui_navigation.hpp

@@ -94,6 +94,7 @@ class NavigationView : public View {
     NavigationView& operator=(NavigationView&&) = delete;
 
     bool is_top() const;
+    bool is_valid() const;
 
     template <class T, class... Args>
     T* push(Args&&... args) {