gpui: Fix busyloop on X disconnect (#41986)

kitt created 

When the connection to X is broken zed will go into an infinite loop and
eat up 100% (of one core) of CPU; this change causes it to exit with an
error instead.

I encountered this behavior while running zed in
[Xephyr](https://freedesktop.org/wiki/Software/Xephyr/) for testing,
though I do sometimes terminate my X server as a way to log out or
attempt to recover from a (very) broken state, and I appreciate a
graceful exit in those situations!

Exiting in case of X server disconnect is common practice in my
observations, likely as the difficulty of recreating state stored
server-side outweighs the potential utility in attempting to recover (if
"reconnecting" to an X server is ever desired in regular usage,
[Xpra](https://xpra.org/index.html) might be able to help!).


Release Notes:

- N/A

Change summary

crates/gpui_linux/src/linux/x11/client.rs | 3 +++
1 file changed, 3 insertions(+)

Detailed changes

crates/gpui_linux/src/linux/x11/client.rs 🔗 

@@ -602,6 +602,9 @@ impl X11Client {
                     Ok(None) => {
                         break;
                     }
+                    Err(err @ ConnectionError::IoError(..)) => {
+                        return Err(EventHandlerError::from(err));
+                    }
                     Err(err) => {
                         let err = handle_connection_error(err);
                         log::warn!("error while polling for X11 events: {err:?}");