Null reference fixes

Subsurface/Source/Characters/Character.cs

@@ -1294,7 +1294,7 @@ namespace Barotrauma
                                 (c2.IsRemotePlayer || c2 == GameMain.Server.Character) && 
                                 Vector2.Distance(c2.WorldPosition, c.WorldPosition) < NetConfig.CharacterIgnoreDistance);
                     }
-                    else
+                    else if (Submarine.MainSub != null)
                     {
                         //disable AI characters that are far away from the sub and the controlled character
                         c.Enabled = Vector2.Distance(Submarine.MainSub.WorldPosition, c.WorldPosition) < NetConfig.CharacterIgnoreDistance ||

Subsurface/Source/Map/Explosion.cs

@@ -93,7 +93,7 @@ namespace Barotrauma
 
                     item.ApplyStatusEffects(ActionType.OnFire, 1.0f);
 
-                    if (item.Condition <= 0.0f)
+                    if (item.Condition <= 0.0f && GameMain.Server != null)
                     {
                         GameMain.Server.CreateEntityEvent(item, new object[] { NetEntityEvent.Type.ApplyStatusEffect, ActionType.OnFire });
                     }

Subsurface/Source/Map/FireSource.cs

@@ -280,7 +280,7 @@ namespace Barotrauma
                 if (item.Position.Y < position.Y - size.Y || item.Position.Y > hull.Rect.Y) continue;
 
                 item.ApplyStatusEffects(ActionType.OnFire, deltaTime);
-                if (item.Condition <= 0.0f)
+                if (item.Condition <= 0.0f && GameMain.Server != null)
                 {
                     GameMain.Server.CreateEntityEvent(item, new object[] { NetEntityEvent.Type.ApplyStatusEffect, ActionType.OnFire });
                 }

Subsurface/Source/Map/MapEntity.cs

@@ -382,8 +382,8 @@ namespace Barotrauma
             {
                 item.Update(cam, deltaTime);
             }
-
-            Entity.Spawner.Update();
+            
+            Spawner?.Update();
         }
 
         public virtual void Update(Camera cam, float deltaTime) { }