[FIX] account: reconciliation widget: empty line should open write off

In manual reconciliation, have an accound with no direct proposal.
An empty line should be present

Click on it

Before this commit, there was a traceback

After this commit, a write-off creation appears

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

@@ -406,7 +406,8 @@ var LineRenderer = Widget.extend(FieldManagerMixin, {
 
         // mv_lines
         var $mv_lines = this.$('.match table tbody').empty();
-        _.each(state.mv_lines.slice(0, state.limitMoveLines), function (line) {
+        var stateMvLines = state.mv_lines || [];
+        _.each(stateMvLines.slice(0, state.limitMoveLines), function (line) {
             var $line = $(qweb.render("reconciliation.line.mv_line", {'line': line, 'state': state}));
             if (!isNaN(line.id)) {
                 $('<span class="line_info_button fa fa-info-circle"/>')
@@ -415,9 +416,9 @@ var LineRenderer = Widget.extend(FieldManagerMixin, {
             }
             $mv_lines.append($line);
         });
-        this.$('.match .fa-chevron-right').toggleClass('disabled', state.mv_lines.length <= state.limitMoveLines);
+        this.$('.match .fa-chevron-right').toggleClass('disabled', stateMvLines.length <= state.limitMoveLines);
         this.$('.match .fa-chevron-left').toggleClass('disabled', !state.offset);
-        this.$('.match').css('max-height', !state.mv_lines.length && !state.filter.length ? '0px' : '');
+        this.$('.match').css('max-height', !stateMvLines.length && !state.filter.length ? '0px' : '');
 
         // balance
         this.$('.popover').remove();

addons/account/static/tests/reconciliation_tests.js

@@ -1760,5 +1760,43 @@ QUnit.module('account', {
 
         clientAction.destroy();
     });
+
+    QUnit.test('Manual Reconciliation: No lines for account', function (assert) {
+        assert.expect(2);
+
+        var clientAction = new ReconciliationClientAction.ManualAction(null, this.params.options);
+        testUtils.addMockEnvironment(clientAction, {
+            data: this.params.data,
+            session: {
+                currencies: {
+                    3: {
+                        digits: [69, 2],
+                        position: "before",
+                        symbol: "$"
+                    }
+                }
+            },
+        });
+
+        clientAction.appendTo($('#qunit-fixture'));
+
+        // The second reconciliation "line" is where it happens
+        var widget = clientAction.widgets[1];
+
+        var emptyLine = widget.$('tr.mv_line');
+
+        assert.notOk('data-line-id' in emptyLine.getAttributes(),
+            'Empty line should be empty');
+
+        emptyLine.find('td:first').click();
+
+        // Check that a create form is here
+        var writeOffCreate = widget.$('div.create .create_account_id');
+
+        assert.equal(writeOffCreate.length, 1,
+            'A write-off creation should be present');
+
+        clientAction.destroy();
+    });
 });
 });