[bugfix] Leaky trigger state when XQuery method not found

XQuery trigger not found is acceptable behaviour (logs a debug message only, could get very chatty logs otherwise).
BUT the exit path from the exception fails to tidy up the per-thread trigger state. This has been observed to leak memory; the per-thread doesn’t get cleaned up until the thread is deleted, and the trigger cyclic-check stack just builds up.

So we clean up the trigger state when a trigger is not found.

Closes eXist-db#5459

exist-core/src/main/java/org/exist/collections/triggers/XQueryTrigger.java

@@ -451,6 +451,7 @@ private void execute(final TriggerPhase phase, final TriggerEvent event, final D
 					if (LOG.isDebugEnabled()) {
 						LOG.debug("No such function '" + functionName + "' in XQueryTrigger: " + compiledQuery.getSource());
 					}
+					TriggerStatePerThread.clearIfFinished(phase);
 					return;
 				}
 			}