Clean up comments, USB flash, NULLs

Marlin/src/lcd/dogm/marlinui_DOGM.cpp

@@ -423,7 +423,7 @@ void MarlinUI::clear_lcd() { } // Automatically cleared by Picture Loop
     if (onpage) lcd_put_u8str_ind_P(0, baseline, pstr, itemIndex, itemString);
 
     // If a value is included, print a colon, then print the value right-justified
-    if (value != nullptr) {
+    if (value) {
       lcd_put_wchar(':');
       if (extra_row) {
         // Assume that value is numeric (with no descender)