Cannot configure Docker container after being placed on the topology view GNS3 3.0.0 alpha 1

[cristian-ciobanu]

Describe the bug
Cannot configure Docker container after being placed on the topology view

GNS3 version and operating system (please complete the following information):

• OS: ArchLinux
• GNS3 version: 3.0.0 alpha 1
• GNS3 server and GUI are running on same machine (bare metal)

To Reproduce
Steps to reproduce the behavior:

1. Drag a Docker container from the All devices pane on the topology view
2. Right click on the Docker container and choose from Configure from the menu.
3. No configuration dialog box is being opened and the following exception is thrown:

Traceback (most recent call last):
  File "/usr/lib/python3.10/site-packages/gns3/graphics_view.py", line 1046, in configureActionSlot
    self.configureSlot(items)
  File "/usr/lib/python3.10/site-packages/gns3/graphics_view.py", line 686, in configureSlot
    node_properties = NodePropertiesDialog(items, self._main_window)
  File "/usr/lib/python3.10/site-packages/gns3/dialogs/node_properties_dialog.py", line 54, in __init__
    self._loadNodeItems()
  File "/usr/lib/python3.10/site-packages/gns3/dialogs/node_properties_dialog.py", line 94, in _loadNodeItems
    self.showConfigurationPageSlot(item, 0)
  File "/usr/lib/python3.10/site-packages/gns3/dialogs/node_properties_dialog.py", line 132, in showConfigurationPageSlot
    page.loadSettings(item.settings(), item.node())
  File "/usr/lib/python3.10/site-packages/gns3/modules/docker/pages/docker_vm_configuration_page.py", line 115, in loadSettings
    self._custom_adapters = settings["custom_adapters"].copy()
AttributeError: 'NoneType' object has no attribute 'copy'

Screenshots or videos
None

Additional context
None

[grossmj]

Fixed