Widgetbook app throws exception when theme is toggled

[jenshor]

If only one theme is defined, the Widgetbook app throws flutter exceptions when toggling the theme. The app continues running, but the exceptions are distracting - especially if you have debugging of packages enabled.

Packages

• widgetbook

the error occurred in combination with widgetbook_generator but there is no reason to believe this is actually caused by the widgetbook_generator package.

Suggested solution

• Disable the toggle Theme button if only one theme is defined
  It doesnt really make sense to default to the default theme of widgetbook.
• Add a tooltip explaining why the button is enabled
• Start the Widgetbook app in the theme that was defined (currently always defaults to dark theme)