Fix SC_WORLD_LOADED/UNLOADED now that loading and saving takes many f…

…rames.

During the loading or saving screen, consider the map and world as not
loaded, because they are likely only partially valid. This fixes errors
from the log-region script.

library/Core.cpp

@@ -61,6 +61,8 @@ using namespace DFHack;
 #include "df/world_data.h"
 #include "df/interfacest.h"
 #include "df/viewscreen_dwarfmodest.h"
+#include "df/viewscreen_loadgamest.h"
+#include "df/viewscreen_savegamest.h"
 #include <df/graphic.h>
 
 #include <stdio.h>
@@ -1268,10 +1270,23 @@ void Core::doUpdate(color_ostream &out, bool first_update)
     if (first_update)
         onStateChange(out, SC_CORE_INITIALIZED);
 
+    // find the current viewscreen
+    df::viewscreen *screen = NULL;
+    if (df::global::gview)
+    {
+        screen = &df::global::gview->view;
+        while (screen->child)
+            screen = screen->child;
+    }
+
+    bool is_load_save =
+        strict_virtual_cast<df::viewscreen_loadgamest>(screen) ||
+        strict_virtual_cast<df::viewscreen_savegamest>(screen);
+
     // detect if the game was loaded or unloaded in the meantime
     void *new_wdata = NULL;
     void *new_mapdata = NULL;
-    if (df::global::world)
+    if (df::global::world && !is_load_save)
     {
         df::world_data *wdata = df::global::world->world_data;
         // when the game is unloaded, world_data isn't deleted, but its contents are
@@ -1313,16 +1328,10 @@ void Core::doUpdate(color_ostream &out, bool first_update)
     }
 
     // detect if the viewscreen changed
-    if (df::global::gview) 
+    if (screen != top_viewscreen)
     {
-        df::viewscreen *screen = &df::global::gview->view;
-        while (screen->child)
-            screen = screen->child;
-        if (screen != top_viewscreen) 
-        {
-            top_viewscreen = screen;
-            onStateChange(out, SC_VIEWSCREEN_CHANGED);
-        }
+        top_viewscreen = screen;
+        onStateChange(out, SC_VIEWSCREEN_CHANGED);
     }
 
     if (df::global::pause_state)