Various crash fixes.

src/pathfinding.rs

@@ -1,6 +1,7 @@
 use std::collections::HashMap;
 
 use bevy::{
+    ecs::entity::Entities,
     prelude::*,
     tasks::{prelude::*, Task},
 };
@@ -258,10 +259,16 @@ fn poll_tasks(mut commands: Commands, mut query: Query<(Entity, &mut Calculating
     }
 }
 
-fn remove_destination(mut commands: Commands, removed: RemovedComponents<Destination>) {
+fn remove_destination(
+    mut commands: Commands,
+    entities: &Entities,
+    removed: RemovedComponents<Destination>,
+) {
     for entity in removed.iter() {
+        if entities.contains(entity) {
             commands.entity(entity).remove::<Calculating>();
         }
+    }
 }
 
 fn negotiate_path(

src/visibility.rs

@@ -314,7 +314,7 @@ fn remove_visible(
                 continue;
             }
             visible_entities.remove(&removed);
-            let map = map.single();
+            if let Ok(map) = map.get_single() {
                 let mut cache = HashMap::new();
                 viewshed.update(
                     &viewer_entity,
@@ -329,6 +329,7 @@ fn remove_visible(
                 );
             }
         }
+    }
 }
 
 fn update_revealed_tiles(