Provide visual feedback if Vuex state does not load due to error

[mtimoustafa]

What problem does this feature solve?

Currently in the Vuex pane, loading the state might silently fail without providing any visual feedback if there is an error somewhere in the store. An error is logged to console, but the message "Loading state" is still visible, along with a spinner.

This has created a lot of user confusion, as seen in issues #967 and #773.

What does the proposed API look like?

It would be much less confusing if, for example, the "Loading state" message was removed and replaced by an error message asking you to check the console for a store error.

A similar case can be found when right clicking on an element on a page and selecting "Inspect Vue component", which will prompt a message at the bottom of the screen asking you to open the Vue tab on dev tools if it isn't already open. This helps eliminate user confusion and cut down on time wasted investigating the 'issue'.

Thanks!