don't use the IItemStackList#add in IItemStackList#copy, same for IFluidStackList, #501

src/main/java/com/raoulvdberge/refinedstorage/apiimpl/util/FluidStackList.java

@@ -101,7 +101,7 @@ public class FluidStackList implements IFluidStackList {
         FluidStackList list = new FluidStackList();
 
         for (FluidStack stack : stacks.values()) {
-            list.add(stack.copy());
+            list.stacks.put(stack.getFluid(), stack.copy());
         }
 
         return list;

src/main/java/com/raoulvdberge/refinedstorage/apiimpl/util/ItemStackList.java

@@ -107,7 +107,7 @@ public class ItemStackList implements IItemStackList {
         ItemStackList list = new ItemStackList();
 
         for (ItemStack stack : stacks.values()) {
-            list.add(stack.copy());
+            list.stacks.put(stack.getItem(), stack.copy());
         }
 
         return list;