pause: Fix infinite loop in filament stuck logic with MMU

When the filament is stuck on a printer with MMU (e.g. MK4S), the firmware would enter an infinite loop in the pause state machine because 'LoadType::filament_stuck' was not handled in 'mmu_unload_start_process'.

This change adds the missing case to allow the MMU to unload and eject the stuck filament.

Author: m42e

src/marlin_stubs/pause/pause.cpp

@@ -714,7 +714,7 @@ void Pause::mmu_load_start_process([[maybe_unused]] Response response) {
 
         setPhase(PhasesLoadUnload::IsColor);
         set(LoadState::color_correct_ask);
-    } else if (load_type == LoadType::filament_change) {
+    } else if (load_type == LoadType::filament_change || load_type == LoadType::filament_stuck) {
         if (settings.mmu_filament_to_load == MMU2::FILAMENT_UNKNOWN) {
             set(LoadState::load_prime);
             return;
@@ -750,7 +750,7 @@ void Pause::mmu_unload_start_process([[maybe_unused]] Response response) {
     if (load_type == LoadType::unload) {
         MMU2::mmu2.unload();
         set(LoadState::_finished);
-    } else if (load_type == LoadType::filament_change) {
+    } else if (load_type == LoadType::filament_change || load_type == LoadType::filament_stuck) {
         settings.mmu_filament_to_load = MMU2::mmu2.get_current_tool();
 
         // No filament loaded in MMU, we can't continue, as we don't know what slot to load