[FIX] account: default_get aml compute balance

Create an account.move, create a line, then add an item to start to add a second aml
The current balance of the move is put in debit (or credit) to help automatically making the second line

Save the move.
Edit the move
Delete a line
Add a new line

Before this commit, the balance was not correctly computed because the default_get did not compute
the balance on deleted lines
The move ended up with wrong unbalanced new lines

After this commit, the balance is computed with deleted lines taken into account

addons/account/models/account_move.py

@@ -475,8 +475,11 @@ class AccountMoveLine(models.Model):
         #compute the default credit/debit of the next line in case of a manual entry
         balance = 0
         for line in self._context['line_ids']:
-            if line[2]:
+            if line[2]:  # in case of command 0: add a record with values
                 balance += line[2].get('debit', 0) - line[2].get('credit', 0)
+            elif line[0] == 2:  # line has been deleted
+                line_obj = self.browse(line[1])
+                balance -= line_obj.debit - line_obj.credit
         if balance < 0:
             rec.update({'debit': -balance})
         if balance > 0: