Ignore homing button when SD printing

As suggested in #5404 by @android444

Marlin/Marlin_main.cpp

@@ -9972,7 +9972,7 @@ void manage_inactivity(bool ignore_stepper_queue/*=false*/) {
     // ---------------------------------------------------------
     static int homeDebounceCount = 0;   // poor man's debouncing count
     const int HOME_DEBOUNCE_DELAY = 2500;
-    if (!READ(HOME_PIN)) {
+    if (!IS_SD_PRINTING && !READ(HOME_PIN)) {
       if (!homeDebounceCount) {
         enqueue_and_echo_commands_P(PSTR("G28"));
         LCD_MESSAGEPGM(MSG_AUTO_HOME);