[FIX] account: traceback in reconciliation widget

If a user reconcile an active line, when he active an other line, the
widget can't close the removed line because it no longer exists.

bug introduce by https://github.com/odoo/odoo/commit/1de418aa7afb986eeb2b98f12dee0c5661902737

addons/account/static/src/js/reconciliation/reconciliation_action.js

@@ -201,7 +201,10 @@ var StatementAction = Widget.extend(ControlPanelMixin, {
                 _.each(self.model.lines, function (line, _handle) {
                     if (line.mode !== 'inactive' && _handle !== handle) {
                         self.model.changeMode(_handle, 'inactive');
-                        self._getWidget(_handle).update(line);
+                        var widget = self._getWidget(_handle);
+                        if (widget) {
+                            widget.update(line);
+                        }
                     }
                 });
             }

addons/account/static/tests/reconciliation_tests.js

@@ -1005,7 +1005,6 @@ QUnit.module('account', {
         clientAction.destroy();
     });
 
-
     QUnit.test('Reconciliation pager', function (assert) {
         assert.expect(6);
 
@@ -1219,9 +1218,11 @@ QUnit.module('account', {
 
         assert.strictEqual(clientAction.$('.o_reconciliation_line').length, 10, "should display 10 lines");
         assert.strictEqual(clientAction.$('.js_load_more:visible').length, 1, "should display the load more button");
+        clientAction.$('.accounting_view:has(.o_reconcile:visible) thead .cell_action').click();
         clientAction.$('.o_reconcile:visible').click();
         assert.strictEqual(clientAction.$('.o_reconcile:visible').length, 0, "should remove the reconciled line");
         assert.strictEqual(clientAction.$('.o_reconciliation_line').length, 10, "should load one line to complete the 10");
+        clientAction.$('thead .cell_action:eq(1)').click();
         clientAction.$('.js_load_more').click();
         assert.strictEqual(clientAction.$('.o_reconciliation_line').length, 11, "should load the last record");
         assert.strictEqual(clientAction.$('.js_load_more:visible').length, 0, "should hide the load more button");