Add friend action error messages don't show up if passed invalid guid

[brettp]

Current Error message includes user name of friended entity. No logic to handle if a guid isn't valid.

[cash]

This would happen if a user was deleted/disabled between another user requesting a page and clicking "add friend". Any other ways for this to happen?

I'm not inclined to create a special error message for something that is so unlikely. Maybe some kind of missing parameter error or an access error.

Also, we need to remove the "please try again" from Elgg's error messages. If something fails once, it is not likely to work the second time. Encouraging users to do something futile is not a good idea.

[brettp]

I caught this while documenting the JS engine's elgg.action(). I accidentally passed the wrong parameter and instead of giving any error it just looked like the ajax never fired.

[Cash Costello]

Fixes #4348 adds check for missing user when friending

Changeset: bdb32999ac9bcdce8803868fb7f400ddc8db8cbd

[Cash Costello]

Fixes #4348 adds check for missing user when friending

Changeset: bdb32999ac9bcdce8803868fb7f400ddc8db8cbd