Fixed|XG: Player armor set to limit when triggering XG 'power' class …

…lines

Due to refactoring oversight back in 2009, the logic of the XG power
line class was changed to the effect that the player's armor value
would be set to the min/max limit if the amount of armor to give/take
was above/below that which the player currently has.

IssueID #906

doomsday/plugins/common/src/p_xgline.cpp

@@ -1620,13 +1620,11 @@ int XL_DoPower(Line * /*line*/, dd_bool /*ceiling*/, void * /*context*/,
     void *context2, mobj_t *activator)
 {
     linetype_t *info = static_cast<linetype_t *>(context2);
-    player_t *player = 0;
-    int delta;
+    DENG2_ASSERT(info);
+    player_t *player = activator? activator->player : nullptr;
 
-    if(activator)
-        player = activator->player;
-
-    if(!player) // Must be a player.
+    // Only players have armor.
+    if(!player)
     {
 /*        if(evtype == XLE_FUNC)
             LOG_MAP_MSG_XGDEVONLY("Sector Functions don't have activators! Use a Sector Chain instead");
@@ -1636,16 +1634,16 @@ int XL_DoPower(Line * /*line*/, dd_bool /*ceiling*/, void * /*context*/,
         return false;
     }
 
-    delta = XG_RandomInt(info->iparm[0], info->iparm[1]);
+    int delta = XG_RandomInt(info->iparm[0], info->iparm[1]);
     if(delta > 0)
     {
         if(player->armorPoints + delta >= info->iparm[3])
-            delta = info->iparm[3] - player->armorPoints;
+            delta = de::max(0, info->iparm[3] - player->armorPoints);
     }
     else
     {
         if(player->armorPoints + delta <= info->iparm[2])
-            delta = info->iparm[2] - player->armorPoints;
+            delta = de::min(0, info->iparm[2] - player->armorPoints);
     }
 
     if(delta)