- SW: avoid crashing when unwinding from a savegame loading error.

The linked list may be incomplete in this case.
Also kept the macro unmangling done to debug this code.

source/games/sw/src/lists.h

@@ -56,9 +56,11 @@ typedef
                                     ((LIST)  list)->Prev = (LIST) nodep,        \
                                     ((LIST) nodep)->Prev->Next = (LIST) nodep)
 
-#define REMOVE(nodep)        ( ((LIST) nodep)->Prev->Next = ((LIST) nodep)->Next, \
-                               ((LIST) nodep)->Next->Prev = ((LIST) nodep)->Prev)
-
+inline void REMOVE(PANEL_SPRITEp nodep)
+{
+    nodep->Prev->Next = nodep->Next;
+    nodep->Next->Prev = nodep->Prev;
+}
 
 #define TRAVERSE(l, o, n)    ASSERT(((LIST)l)->Next && ((LIST)l)->Prev); for (o = (decltype(o))(((LIST)l)->Next);      \
                                                                               n = o->Next, (LIST) o != (LIST) l; \

source/games/sw/src/panel.cpp

@@ -6513,9 +6513,11 @@ void
 pClearSpriteList(PLAYERp pp)
 {
     PANEL_SPRITEp psp=nullptr, next_psp=nullptr;
+    auto l = &pp->PanelSpriteList;
 
-    TRAVERSE(&pp->PanelSpriteList, psp, next_psp)
+    for (psp = l->Next; next_psp = psp->Next, (LIST)psp != (LIST)l; psp = next_psp)
     {
+        if (psp->Next == nullptr || psp->Prev == nullptr) return; // this can happen when cleaning up a fatal error.
         pKillSprite(psp);
     }
 }