Bunch of crew AI bugfixes/improvements:

- replacing empty oxygen tanks
- fixed characters only fixing leaks in the outer hull
- prioritizing large leaks over small ones
- fixed characters doing nothing after fixing all the leaks (and sinking to the bottom if they happen to be outside)
- more accurate welder aiming
- AIObjectiveGetItem makes the characters go to the cabinet/container an item is inside, not to the actual item (which may not be actually positioned at the container)

Subsurface/Source/Characters/AI/Objectives/AIObjectiveFixLeaks.cs

@@ -1,4 +1,5 @@
-using Microsoft.Xna.Framework;
+using System;
+using Microsoft.Xna.Framework;
 using System.Collections.Generic;
 using System.Linq;
 
@@ -10,6 +11,8 @@ namespace Barotrauma
 
         private float updateGapListTimer;
 
+        private AIObjectiveIdle idleObjective;
+
         private List<AIObjectiveFixLeak> objectiveList;
 
         public AIObjectiveFixLeaks(Character character)
@@ -36,13 +39,19 @@ namespace Barotrauma
 
             if (objectiveList.Any())
             {
-                objectiveList[objectiveList.Count-1].TryComplete(deltaTime);
+                objectiveList[objectiveList.Count - 1].TryComplete(deltaTime);
 
-                if (!objectiveList[objectiveList.Count-1].CanBeCompleted || objectiveList[objectiveList.Count-1].IsCompleted())
+                if (!objectiveList[objectiveList.Count - 1].CanBeCompleted ||
+                    objectiveList[objectiveList.Count - 1].IsCompleted())
                 {
                     objectiveList.RemoveAt(objectiveList.Count - 1);
                 }
             }
+            else
+            {
+                if (idleObjective == null) idleObjective = new AIObjectiveIdle(character);
+                idleObjective.TryComplete(deltaTime);
+            }
         }
 
         private void UpdateGapList()
@@ -51,13 +60,14 @@ namespace Barotrauma
             
             foreach (Gap gap in Gap.GapList)
             {
-                if (gap.IsRoomToRoom || gap.ConnectedDoor != null || gap.Open < 0.1f) continue;
+                if (gap.ConnectedWall == null) continue;
+                if (gap.ConnectedDoor != null || gap.Open <= 0.0f) continue;
 
-                float dist = Vector2.DistanceSquared(character.WorldPosition, gap.WorldPosition);
+                float gapPriority = GetGapFixPriority(gap);
 
                 int index = 0;
-                while (index<objectiveList.Count && 
-                    Vector2.DistanceSquared(objectiveList[index].Leak.WorldPosition, character.WorldPosition)>dist)
+                while (index < objectiveList.Count &&
+                    GetGapFixPriority(objectiveList[index].Leak) < gapPriority)
                 {
                     index++;
                 }
@@ -66,6 +76,23 @@ namespace Barotrauma
             }
         }
 
+        private float GetGapFixPriority(Gap gap)
+        {
+            if (gap == null) return 0.0f;
+
+            //larger gap -> higher priority
+            float gapPriority = (gap.isHorizontal ? gap.Rect.Width : gap.Rect.Height) * gap.Open;
+
+            //prioritize gaps that are close
+            gapPriority /= Math.Max(Vector2.Distance(character.WorldPosition, gap.WorldPosition), 1.0f);
+
+            //gaps to outside are much higher priority
+            if (!gap.IsRoomToRoom) gapPriority *= 10.0f;
+
+            return gapPriority;
+
+        }
+
         public override bool IsDuplicate(AIObjective otherObjective)
         {
             return otherObjective is AIObjectiveFixLeaks;