[mu4e] Catch errors when loading org

[fnussbaum]

An error within (with-eval-after-load 'org ...) has severe consequences: Org fails to load, and also help buffers cannot be opened at all, due to the elisp-demos package requiring org.

[bcc32]

What error from mu4e did you see here?

Because of #16871 I'm a little wary of introducing uses of
with-demoted-errors; shouldn't the user just be made to see the
error and either debug it or disable mu4e-org-link-support?

[fnussbaum]

This raises an error when mu4e is not properly installed, but the layer is added, for example.

Because of #16871 I'm a little wary of introducing uses of
with-demoted-errors;

Fair point, but I'd actually like to catch even more errors (see #16952), at least on startup, where they often make Spacemacs completely unusable. I think having to set debug-on-error to get a backtrace in some more cases is an acceptable trade-off for having a usable editor, which can be used to investigate, solve, or report those startup errors. (For me personally, at least, encountering uncaught errors on startup has been a common source of frustration in the past.)

Also, in this case the error usually occurs (or can easily be reproduced) during a session, which means toggle-debug-on-error will produce a backtrace.

shouldn't the user just be made to see the
error and either debug it or disable mu4e-org-link-support?

With this change, the user should still see the error; but I can make it even more visible by using configuration-layer//error which would make it show up on the Spacemacs buffer, if you prefer. I don't think we should "artificially" make errors more severe by letting them break unrelated functionality such as in this case.

[bcc32]

Ah, right, I misunderstood and now realize that this error does not actually occur at startup but instead afterwards. LGTM.