unconfigured secrets provider crashes k8t

[afriemann]

on a fresh environment when running k8t gen without configuring secrets provider this happens:

Traceback (most recent call last):
  File "/nix/store/clp0r685d4ivm5wydqnffzcx68vpvxmc-k8t-0.4.3/bin/.k8t-wrapped", line 9, in <module>
    sys.exit(main())
  File "/nix/store/clp0r685d4ivm5wydqnffzcx68vpvxmc-k8t-0.4.3/lib/python3.7/site-packages/k8t/cli.py", line 284, in main
    root()  # pylint: disable=no-value-for-parameter
  File "/nix/store/02mkfzlja90abihab4fxg2kwz9z8aly7-python3.7-click-7.0/lib/python3.7/site-packages/click/core.py", line 764, in __call__
    return self.main(*args, **kwargs)
  File "/nix/store/02mkfzlja90abihab4fxg2kwz9z8aly7-python3.7-click-7.0/lib/python3.7/site-packages/click/core.py", line 717, in main
    rv = self.invoke(ctx)
  File "/nix/store/02mkfzlja90abihab4fxg2kwz9z8aly7-python3.7-click-7.0/lib/python3.7/site-packages/click/core.py", line 1137, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/nix/store/02mkfzlja90abihab4fxg2kwz9z8aly7-python3.7-click-7.0/lib/python3.7/site-packages/click/core.py", line 956, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/nix/store/02mkfzlja90abihab4fxg2kwz9z8aly7-python3.7-click-7.0/lib/python3.7/site-packages/click/core.py", line 555, in invoke
    return callback(*args, **kwargs)
  File "/nix/store/02mkfzlja90abihab4fxg2kwz9z8aly7-python3.7-click-7.0/lib/python3.7/site-packages/click/decorators.py", line 17, in new_func
    return f(get_current_context(), *args, **kwargs)
  File "/nix/store/clp0r685d4ivm5wydqnffzcx68vpvxmc-k8t-0.4.3/lib/python3.7/site-packages/k8t/cli.py", line 32, in new_func
    return ctx.invoke(func, *args, **kwargs)
  File "/nix/store/02mkfzlja90abihab4fxg2kwz9z8aly7-python3.7-click-7.0/lib/python3.7/site-packages/click/core.py", line 555, in invoke
    return callback(*args, **kwargs)
  File "/nix/store/clp0r685d4ivm5wydqnffzcx68vpvxmc-k8t-0.4.3/lib/python3.7/site-packages/k8t/cli.py", line 129, in cli_gen
    config.CONFIG['secrets']['provider'] = secret_provider
KeyError: 'secrets'