[automation] Avoid memory leak on script loading failure (#4162)

Core part of the fix for openhab/openhab-addons#16462.

Signed-off-by: Florian Hotze <[email protected]>

bundles/org.openhab.core.automation.module.script/src/main/java/org/openhab/core/automation/module/script/internal/ScriptEngineManagerImpl.java

@@ -175,7 +175,13 @@ public boolean loadScript(String engineIdentifier, InputStreamReader scriptData)
                 return true;
             } catch (Exception ex) {
                 logger.error("Error during evaluation of script '{}': {}", engineIdentifier, ex.getMessage());
-                logger.debug("", ex);
+                // Only call logger if debug level is actually enabled, because OPS4J Pax Logging holds (at least for
+                // some time) a reference to the exception and its cause, which may hold a reference to the script
+                // engine.
+                // This prevents garbage collection (at least for some time) to remove the script engine from heap.
+                if (logger.isDebugEnabled()) {
+                    logger.debug("", ex);
+                }
             }
         }
         return false;