- Make old-nextwalls invalid on the following two occasions: ovh_whiteoutgrab

with no highlighted sectors; and when entering 3D mode, even if there are
  highlighted sectors. This should have almost no effect, but I find it cleaner
  that way.
- Check map for corruption every time an editing change is done. This was
  accidentally disabled when commenting out the undo code (which I've yet
  to debug).

git-svn-id: https://svn.eduke32.com/eduke32@2121 1a8010ca-5511-0410-912e-c29ae57300e0

polymer/eduke32/build/src/build.c

@@ -1621,7 +1621,10 @@ void ovh_whiteoutgrab(int32_t restoreredwalls)
             wall[j].nextsector = -1;
         }
 
-    mkonwvalid();
+    if (highlightsectorcnt > 0)
+        mkonwvalid();
+    else
+        mkonwinvalid();
 }
 
 static void duplicate_selected_sectors(void)
@@ -6896,6 +6899,7 @@ CANCEL:
             checksectorpointer(j, highlightsector[i]);
         }
     }
+    mkonwinvalid();
 
     fixspritesectors();
 

polymer/eduke32/source/astub.c

@@ -11290,6 +11290,8 @@ void ExtCheckKeys(void)
         {
 #if M32_UNDO
             create_map_snapshot();
+#else
+            CheckMapCorruption(6, 0);
 #endif
             asksave++;
         }