v0.6.3a: fixed various rare crashes with the alchemy window

core/src/main/java/com/shatteredpixel/shatteredpixeldungeon/windows/WndAlchemy.java

@@ -86,6 +86,7 @@ public class WndAlchemy extends Window {
 		
 		h += desc.height() + 6;
 
+		synchronized (inputs) {
 			for (int i = 0; i < inputs.length; i++) {
 				inputs[i] = new WndBlacksmith.ItemButton() {
 					@Override
@@ -105,6 +106,7 @@ public class WndAlchemy extends Window {
 				add(inputs[i]);
 				h += BTN_SIZE + 2;
 			}
+		}
 		
 		btnCombine = new RedButton(""){
 			Image arrow;
@@ -211,7 +213,8 @@ public class WndAlchemy extends Window {
 	protected WndBag.Listener itemSelector = new WndBag.Listener() {
 		@Override
 		public void onSelect( Item item ) {
-			if (item != null) {
+			synchronized (inputs) {
+				if (item != null && inputs[0] != null) {
 					for (int i = 0; i < inputs.length; i++) {
 						if (inputs[i].item == null) {
 							if (item instanceof Dart) {
@@ -222,9 +225,10 @@ public class WndAlchemy extends Window {
 							break;
 						}
 					}
-			}
 					updateState();
 				}
+			}
+		}
 	};
 	
 	private<T extends Item> ArrayList<T> filterInput(Class<? extends T> itemClass){
@@ -276,8 +280,9 @@ public class WndAlchemy extends Window {
 				Dungeon.level.drop(result, Dungeon.hero.pos);
 			}
 
+			synchronized (inputs) {
 				for (int i = 0; i < inputs.length; i++) {
-				if (inputs[i].item != null)  {
+					if (inputs[i] != null && inputs[i].item != null) {
 						if (inputs[i].item.quantity() <= 0) {
 							inputs[i].slot.item(new WndBag.Placeholder(ItemSpriteSheet.SOMETHING));
 							inputs[i].item = null;
@@ -286,6 +291,7 @@ public class WndAlchemy extends Window {
 						}
 					}
 				}
+			}
 			
 			btnCombine.enable(false);
 		}