Fix: TraceIgnorePathPatterns can't set empty value (#7059)

CHANGES.md

@@ -33,6 +33,7 @@ Release Notes.
 * Fix ClassCast issue for RequestHolder/ResponseHolder.
 * fixed `jdk-threading-plugin` memory leak.
 * Optimize multiple field reflection operation in Feign plugin.
+* Fix `trace-ignore-plugin` TraceIgnorePathPatterns can't set empty value
 
 #### OAP-Backend
 * BugFix: filter invalid Envoy access logs whose socket address is empty.

apm-sniffer/optional-plugins/trace-ignore-plugin/src/main/java/org/apache/skywalking/apm/plugin/trace/ignore/TraceIgnoreExtendService.java

@@ -89,6 +89,8 @@ public class TraceIgnoreExtendService extends SamplingService {
     void handleTraceIgnorePatternsChanged() {
         if (StringUtil.isNotBlank(traceIgnorePatternWatcher.getTraceIgnorePathPatterns())) {
             patterns = traceIgnorePatternWatcher.getTraceIgnorePathPatterns().split(PATTERN_SEPARATOR);
+        } else {
+            patterns = new String[] {};
         }
     }
 }