Fix garage door knockback crash (#36671)

src/game.cpp

@@ -5050,18 +5050,19 @@ bool game::forced_door_closing( const tripoint &p, const ter_id &door_type, int
     const std::string &door_name = door_type.obj().name();
     int kbx = x; // Used when player/monsters are knocked back
     int kby = y; // and when moving items out of the way
-    for( int i = 0; i < 20; i++ ) {
-        const int x_ = x + rng( -1, +1 );
-        const int y_ = y + rng( -1, +1 );
-        if( is_empty( {x_, y_, get_levz()} ) ) {
-            // invert direction, as game::knockback needs
-            // the source of the force that knocks back
-            kbx = -x_ + x + x;
-            kby = -y_ + y + y;
-            break;
-        }
+    const auto valid_location = [&]( const tripoint & p ) {
+        return g->is_empty( p );
+    };
+    if( const cata::optional<tripoint> pos = random_point( m.points_in_radius( p, 2 ),
+            valid_location ) ) {
+        kbx = -pos->x + x + x;
+        kby = -pos->y + y + y;
     }
     const tripoint kbp( kbx, kby, p.z );
+    if( kbp == p ) {
+        // cant pushback any creatures anywhere, that means the door cant close.
+        return false;
+    }
     const bool can_see = u.sees( tripoint( x, y, p.z ) );
     player *npc_or_player = critter_at<player>( tripoint( x, y, p.z ), false );
     if( npc_or_player != nullptr ) {