fix(ipc): don't format empty strings (#2549)

* fix(ipc): don't format empty strings

* Add a description of the change to `CHANGELOG.md`

* Rephrasing

CHANGELOG.md

@@ -168,6 +168,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - `include-directory` and `include-file` now support relative paths. The paths
   are relative to the folder of the file where those directives appear.
   ([`#2523`](https://github.com/polybar/polybar/issues/2523))
+- `custom/ipc`: Empty output strings are no longer formatted. This prevents
+  extraneous spaces and separators from appearing in the bar when the output of
+  an ipc module is empty.
 
 ### Fixed
 - `custom/script`: Concurrency issues with fast-updating tailed scripts.

src/modules/ipc.cpp

@@ -90,6 +90,9 @@ namespace modules {
     // the format prefix/suffix also gets wrapper
     // with the cmd handlers
     string output{module::get_output()};
+    if (output.empty()) {
+      return "";
+    }
 
     for (auto&& action : m_actions) {
       if (!action.second.empty()) {