fw/shell: fix dark mode function and stubs

Signed-off-by: Andrew McOlash <amcolash@gmail.com>

Author: amcolash

src/fw/shell/prf/stubs.c

@@ -245,6 +245,14 @@ void shell_prefs_set_language_english(bool english) {
 void shell_prefs_toggle_language_english(void) {
 }
 
+GColor shell_prefs_get_theme_highlight_color(void) {
+  return PBL_IF_COLOR_ELSE(GColorVividCerulean, GColorBlack);
+}
+
+DarkMode shell_prefs_get_dark_mode(void) {
+  return DarkModeOff;
+}
+
 FontInfo *fonts_get_system_emoji_font_for_size(unsigned int font_height) {
   return NULL;
 }

src/fw/shell/system_theme.c

@@ -186,7 +186,11 @@ static bool prv_is_system_app(void) {
 }
 
 bool system_theme_is_dark_mode(void) {
-  if (!PBL_IF_COLOR_ELSE(prv_is_system_app(), false)) {
+  // Dark mode is only supported on color platforms, so treat all non-color platforms as light mode
+  if (PBL_IF_COLOR_ELSE(false, true)) {
+    return false;
+  }
+  if (!prv_is_system_app()) {
     return false;
   }
   switch (shell_prefs_get_dark_mode()) {