'No data to retrieve' prevents `GraphView` from loading

[reelmatt]

If a user tries to load Node data before that Node has been executed, a "Loading data..." message appears behind the visual node. This does not disappear, nor can the user click the "view data" icon, even after execution.

Steps to reproduce:

1. Drag a Read CSV node to the workspace and select a file to read.
2. Click the 'table icon' and choose 'Load'.
3. The server responds with an error message that there's no data to retrieve.
4. The user executes the Node (to create the data to retrieve).
5. User cannot click the 'table icon' and the "Loading data..." message remains in the workspace.

Easiest change is probably to make the 'table icon' disabled until the Node reaches the 'complete' state (green). This would prevent loading data in the following use case:

1. User executes Read CSV.
2. User changes the file/config which changes the node to 'configured' and the 'table icon' disabled.
3. Data still exists from the execution in step 1, but it is not accessible.

but this should be fine, because the data from step 1 is now out-of-date and having the option to view it could lead to confusion.

Screen recording