Stop ant tunnels stomping over other map terrain underground and remo…

…ving staircases (#36702)

* stop ant tunnels stomping over other map terrain underground
* also add check to adjacent loop

src/overmap.cpp

@@ -3218,14 +3218,18 @@ void overmap::build_tunnel( const tripoint &p, int s, om_direction::type dir )
     if( check_ot( "ants", ot_match_type::type, p ) && root_id != ter( p )->id ) {
         return;
     }
+    if( !is_ot_match( "empty_rock", ter( p )->id, ot_match_type::type ) ) {
+        return;
+    }
 
     ter_set( p, oter_id( root_id ) );
 
     std::vector<om_direction::type> valid;
     valid.reserve( om_direction::size );
     for( auto r : om_direction::all ) {
         const tripoint cand = p + om_direction::displace( r );
-        if( !check_ot( "ants", ot_match_type::type, cand ) ) {
+        if( !check_ot( "ants", ot_match_type::type, cand ) &&
+            !is_ot_match( "empty_rock", ter( cand )->id, ot_match_type::type ) ) {
             valid.push_back( r );
         }
     }