fix(script): clear output when exec-if fails (#2675)

Fixes #2674

CHANGELOG.md

@@ -9,6 +9,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+### Fixed
+- `custom/script`: Output clearing when `exec-if` fails ([`#2674`](https://github.com/polybar/polybar/issues/2674))
 
 ## [3.6.2] - 2022-04-03
 ### Fixed

src/adapters/script_runner.cpp

@@ -45,7 +45,10 @@ script_runner::interval script_runner::process() {
 }
 
 void script_runner::clear_output() {
-  set_output("");
+  auto changed = set_output("");
+  if (changed) {
+    m_on_update(m_data);
+  }
 }
 
 void script_runner::stop() {