multiple fixes related to counter-battery fire

megamek/src/megamek/client/ui/swing/OffBoardTargetOverlay.java

@@ -315,7 +315,7 @@ private void handleButtonClick(OffBoardDirection direction) {
                             JOptionPane.QUESTION_MESSAGE, null, SharedUtility
                                     .getDisplayArray(eligibleTargets), null);
             choice = SharedUtility.getTargetPicked(eligibleTargets, input);
-        } else if (eligibleTargets.size() == 1) {
+        } else if ((eligibleTargets.size() == 1) && (eligibleTargets.get(0) != null)) {
             choice = eligibleTargets.get(0);
         } else {
             return;

megamek/src/megamek/client/ui/swing/boardview/BoardView1.java

@@ -6132,13 +6132,15 @@ public String getHexTooltip(MouseEvent e) {
         return txt.toString();
     }
 
-    private ArrayList<ArtilleryAttackAction> getArtilleryAttacksAtLocation(
-            Coords c) {
+    private ArrayList<ArtilleryAttackAction> getArtilleryAttacksAtLocation(Coords c) {
         ArrayList<ArtilleryAttackAction> v = new ArrayList<ArtilleryAttackAction>();
+
         for (Enumeration<ArtilleryAttackAction> attacks = game
                 .getArtilleryAttacks(); attacks.hasMoreElements(); ) {
             ArtilleryAttackAction a = attacks.nextElement();
-            if (a.getTarget(game).getPosition().equals(c)) {
+            Targetable target = a.getTarget(game);
+
+            if ((target != null) && c.equals(target.getPosition())) {
                 v.add(a);
             }
         }

megamek/src/megamek/common/Targetable.java

@@ -17,6 +17,8 @@
 import java.io.Serializable;
 import java.util.Map;
 
+import megamek.common.annotations.Nullable;
+
 public interface Targetable extends Serializable {
     public static final int TYPE_ENTITY = 0;
     public static final int TYPE_HEX_CLEAR = 1;
@@ -151,4 +153,17 @@ default boolean tracksHeat() {
 
     @Override
     int hashCode();
+
+    /**
+     * Utility function used to safely tell whether two Targetables are in the same hex.
+     * Does not throw exceptions in case of nulls.
+     */
+    public static boolean areAtSamePosition(@Nullable Targetable first, @Nullable Targetable second) {
+        if ((first == null) || (second == null) ||
+                (first.getPosition() == null) || (second.getPosition() == null)) {
+            return false;
+        }
+
+        return first.getPosition().equals(second.getPosition());
+    }
 }

megamek/src/megamek/common/weapons/ArtilleryWeaponIndirectFireHandler.java

@@ -396,7 +396,11 @@ else if ((null != bestSpotter) && !(this instanceof ArtilleryWeaponDirectFireHan
             AreaEffectHelper.clearMineFields(targetPos, Minefield.CLEAR_NUMBER_WEAPON, ae, vPhaseReport, game, server);
         }
 
-        if(aaa.getTarget(game).isOffBoard()) {
+        Targetable updatedTarget = aaa.getTarget(game);
+
+        // the attack's target may have been destroyed or fled since the attack was generated
+        // so we need to carry out offboard/null checks against the "current" version of the target.
+        if ((updatedTarget != null) && updatedTarget.isOffBoard()) {
             DamageFalloff df = AreaEffectHelper.calculateDamageFallOff(atype, shootingBA, mineClear);
             int actualDamage = df.damage - (df.falloff * targetPos.distance(target.getPosition()));
             Coords effectiveTargetPos = aaa.getCoords();
@@ -406,7 +410,7 @@ else if ((null != bestSpotter) && !(this instanceof ArtilleryWeaponDirectFireHan
             }
 
             if(actualDamage > 0) {
-                AreaEffectHelper.artilleryDamageEntity((Entity) aaa.getTarget(game), actualDamage, null, 0, false, asfFlak, isFlak, altitude, 
+                AreaEffectHelper.artilleryDamageEntity((Entity) updatedTarget, actualDamage, null, 0, false, asfFlak, isFlak, altitude, 
                     effectiveTargetPos, atype, targetPos, false, ae, null, altitude, vPhaseReport, server);
             }
         } else {

megamek/src/megamek/server/Server.java

@@ -13481,14 +13481,16 @@ private void processAttack(Entity entity, Vector<EntityAction> vector) {
                 boolean firingAtNewHex = false;
                 final ArtilleryAttackAction aaa = (ArtilleryAttackAction) ea;
                 final Entity firingEntity = game.getEntity(aaa.getEntityId());
+                Targetable attackTarget = aaa.getTarget(game);
+
                 for (Enumeration<AttackHandler> j = game.getAttacks(); !firingAtNewHex
                         && j.hasMoreElements(); ) {
                     WeaponHandler wh = (WeaponHandler) j.nextElement();
                     if (wh.waa instanceof ArtilleryAttackAction) {
                         ArtilleryAttackAction oaaa = (ArtilleryAttackAction) wh.waa;
+
                         if ((oaaa.getEntityId() == aaa.getEntityId())
-                            && !oaaa.getTarget(game).getPosition()
-                                .equals(aaa.getTarget(game).getPosition())) {
+                                && !Targetable.areAtSamePosition(oaaa.getTarget(game), attackTarget)) {
                             firingAtNewHex = true;
                         }
                     }