Problem description: It is not possible to change widget type in the widget configuration form after changing Source type to "Map navigation tree" of a Map widget. The following JS error is observed in the console:

Uncaught TypeError: Cannot read property 'dashboardGrid' of undefined
    at updateWidgetConfigDialogue (zabbix.php?action=dashboard.view&new=1:469)
    at HTMLInputElement.onchange (zabbix.php?action=dashboard.view&new=1:1)

Steps to reproduce:

1. Create a new dashboard
2. Click on the "Add widget" placeholder (or button)
3. In the opened widget configuration form select Type = "Map"
4. Set Source type to "Map navigation tree"
5. Attempt to change value of field "Type"

Result: Widget configuration form is not reloaded, JS error appears in the console.
Expected: No error should be observed, widget configuration form should be reloaded, new set of parameters should be available for the selected widget type.

Example: