Include probing/MBL in the PRINTER_ACTIVE check

This prevents to perform disruptive actions during homing or between MBL
probes, which would result in a failure.

Firmware/Marlin.h

@@ -377,7 +377,7 @@ extern uint16_t gcode_in_progress;
 extern LongTimer safetyTimer;
 
 #define PRINT_PERCENT_DONE_INIT   0xff
-#define PRINTER_ACTIVE (IS_SD_PRINTING || is_usb_printing || isPrintPaused || (custom_message_type == CustomMsg::TempCal) || saved_printing || (lcd_commands_type == LcdCommands::Layer1Cal) || mmu_print_saved)
+#define PRINTER_ACTIVE (IS_SD_PRINTING || is_usb_printing || isPrintPaused || (custom_message_type == CustomMsg::TempCal) || saved_printing || (lcd_commands_type == LcdCommands::Layer1Cal) || mmu_print_saved || homing_flag || mesh_bed_leveling_flag)
 
 //! Beware - mcode_in_progress is set as soon as the command gets really processed,
 //! which is not the same as posting the M600 command into the command queue