Also call clear_command_queue for lcd_sdcard_stop

Marlin/Marlin.h

@@ -254,6 +254,7 @@ inline bool IsStopped() { return !Running; }
 bool enqueue_and_echo_command(const char* cmd, bool say_ok=false); //put a single ASCII command at the end of the current buffer or return false when it is full
 void enqueue_and_echo_command_now(const char* cmd); // enqueue now, only return when the command has been enqueued
 void enqueue_and_echo_commands_P(const char* cmd); //put one or many ASCII commands at the end of the current buffer, read from flash
+void clear_command_queue();
 
 void clamp_to_software_endstops(float target[3]);