Fields are not spreading north-west when they shouldn't anymore (#34226)

src/map_field.cpp

@@ -282,7 +282,6 @@ void map::spread_gas( field_entry &cur, const tripoint &p, int percent_spread,
     // Then, spread to a nearby point.
     // If not possible (or randomly), try to spread up
     // Wind direction will block the field spreading into the wind.
-    spread.reserve( 8 );
     // Start at end_it + 1, then wrap around until all elements have been processed.
     for( size_t i = ( end_it + 1 ) % neighs.size(), count = 0 ;
          count != neighs.size();
@@ -297,7 +296,7 @@ void map::spread_gas( field_entry &cur, const tripoint &p, int percent_spread,
     const maptile remove_tile = std::get<0>( maptiles );
     const maptile remove_tile2 = std::get<1>( maptiles );
     const maptile remove_tile3 = std::get<2>( maptiles );
-    if( !zlevels || one_in( spread.size() ) ) {
+    if( !spread.empty() && ( !zlevels || one_in( spread.size() ) ) ) {
         // Construct the destination from offset and p
         if( g->is_sheltered( p ) || windpower < 5 ) {
             gas_spread_to( cur, neighs[ random_entry( spread ) ] );