fix: deleting subscreens resulting in invalid/crashy data

Author: EmilyV99

src/base/dmap.cpp

@@ -1,3 +1,15 @@
 #include "dmap.h"
+#include "subscr.h"
 
 dmap *DMaps;
+
+void dmap::validate_subscreens()
+{
+	if(active_subscreen >= subscreens_active.size())
+		active_subscreen = 0;
+	if(passive_subscreen >= subscreens_passive.size())
+		passive_subscreen = 0;
+	if(overlay_subscreen >= subscreens_overlay.size())
+		overlay_subscreen = 0;
+}
+

src/base/dmap.h

@@ -68,6 +68,8 @@ struct dmap
 	{
 		*this = dmap();
 	}
+	
+	void validate_subscreens();
 };
 
 extern dmap *DMaps;

src/subscr.cpp

@@ -3371,7 +3371,7 @@ void update_subscreens(int32_t dmap)
 		new_sub_indexes[sstOVERLAY] = indx;
 	}
 
-	if(get_qr(qr_OLD_SUBSCR) && new_subscreen_active)
+	if(get_qr(qr_OLD_SUBSCR) && new_subscreen_active && next_active)
 	{
 		next_active->curpage = new_subscreen_active->curpage;
 		next_active->cur_page().cursor_pos = new_subscreen_active->cur_page().cursor_pos;

src/zq/zq_class.cpp

@@ -7527,6 +7527,8 @@ int32_t writedmaps(PACKFILE *f, word version, word build, word start_dmap, word
 
         for(int32_t i=start_dmap; i<start_dmap+dmap_count; i++)
         {
+			DMaps[i].validate_subscreens();
+			
             if(!p_putc(DMaps[i].map,f))
             {
                 new_return(6);

src/zq/zq_subscr.cpp

@@ -2879,14 +2879,20 @@ void delete_subscreen(size_t ind, byte ty)
 			case sstACTIVE:
 				if(DMaps[i].active_subscreen > count)
 					--DMaps[i].active_subscreen;
+				else if(DMaps[i].active_subscreen == count)
+					DMaps[i].active_subscreen = 0;
 				break;
 			case sstPASSIVE:
 				if(DMaps[i].passive_subscreen > count)
 					--DMaps[i].passive_subscreen;
+				else if(DMaps[i].passive_subscreen == count)
+					DMaps[i].passive_subscreen = 0;
 				break;
 			case sstOVERLAY:
 				if(DMaps[i].overlay_subscreen > count)
 					--DMaps[i].overlay_subscreen;
+				else if(DMaps[i].overlay_subscreen == count)
+					DMaps[i].overlay_subscreen = 0;
 				break;
 		}
 	}