fix(ipc): Clear output until initial hook finishes

Before, it just showed '%output%'

Fixes #3131

CHANGELOG.md

@@ -15,6 +15,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 -  i3: Fix duplicated rendering for non-full-width bars ([`#3091`](https://github.com/polybar/polybar/pull/3091), [`#3060`](https://github.com/polybar/polybar/issues/3060))
 - `internal/backlight`: Module could display the literal `%percentage%` token if the backlight reports a value of 0 at startup ([`#3081`](https://github.com/polybar/polybar/pull/3081)) by [@unclechu](https://github.com/unclechu)
 - `internal/tray`: Fix crash during restarting, when tray icons were not removed proberly ([`#3111`](https://github.com/polybar/polybar/issues/3111), [`#3112`](https://github.com/polybar/polybar/pull/3112))
+- `custom/ipc`: Module would display the literal `%output%` token before the initial hook finished executing ([`#3131`](https://github.com/polybar/polybar/issues/3131), [`#3140`](https://github.com/polybar/polybar/pull/3140))
 
 ## [3.7.1] - 2023-11-27
 ### Build

src/modules/ipc.cpp

@@ -79,6 +79,8 @@ namespace modules {
     this->module::start();
     m_mainthread = thread([&] {
       m_log.trace("%s: Thread id = %i", this->name(), concurrency_util::thread_id(this_thread::get_id()));
+      // Initial update to start with an empty output until the initial hook finishes
+      update_output();
       update();
       broadcast();
     });