organize transaction split processing a bit

lib/gnucash/transaction.rb

@@ -14,16 +14,18 @@ module Gnucash
         unless value_parts.size == 2 and value_parts[1] == '100'
           raise "Unexpected value format: #{value_str.inspect}"
         end
+        account_id = split_node.xpath('split:account').text
+        value = value_parts.first.to_i
+        account = @book.find_account_by_id(account_id)
+        unless account
+          raise "Could not find account with ID #{account_id} for transaction #{@id}"
+        end
+        account.add_transaction(self, value)
         {
-          account_id: split_node.xpath('split:account').text,
-          value: value_parts.first.to_i,
+          account_id: account_id,
+          value: value,
         }
       end
-      @splits.each do |split|
-        account = @book.find_account_by_id(split[:account_id])
-        raise "Could not find account with ID #{split[:account_id]} for transaction #{@id}" unless account
-        account.add_transaction(self, split[:value])
-      end
     end
   end
 end