sur/ files not accessible after other actions

[jfranklin9000]

Working through https://urbit.org/docs/using/shell/ I ran into the following:

brand new fakezod:

/-  sole
`sole-effect:sole`[%bel ~]
[%bel ~]

seems to work

/+  react
(react-vale:react %div)
/~zod/home/~2019.4.14..02.48.13..c025/sys/vane/ford:<[4.840 18].[4.840 59]>
-find.react
ford: %slim failed: 
ford: %ride failed to compute type:

expected because lib/react.hoon does not exist (docs should be updated)

`sole-effect:sole`[%bel ~]
/~zod/home/~2019.4.14..02.48.13..c025/sys/vane/ford:<[4.840 18].[4.840 59]>
-find.sole
ford: %slim failed: 
ford: %ride failed to compute type:

not expected as it worked before trying the react stuff

[joemfb]

No :dojo expression will work if you've imported invalid libs (with /+) or surs (with /-). You have to clear any invalid imports to get :dojo back to a working state.

For libs, either of these will work:

> /+
> =lib

For surs:

> /-
> =sur

[joemfb]

Closing in favor of #81 and #577