[fix](fe) Fix `PluginMgr.getActivePluginList` npt (#41466)
```
Exception in thread "AuditEventProcessor" java.lang.NullPointerException: at index 2
at com.google.common.collect.ObjectArrays.checkElementNotNull(ObjectArrays.java:232)
at com.google.common.collect.ObjectArrays.checkElementsNotNull(ObjectArrays.java:222)
at com.google.common.collect.ObjectArrays.checkElementsNotNull(ObjectArrays.java:216)
at com.google.common.collect.ImmutableList.construct(ImmutableList.java:353)
at com.google.common.collect.ImmutableList.copyOf(ImmutableList.java:265)
at org.apache.doris.plugin.PluginMgr.getActivePluginList(PluginMgr.java:300)
at org.apache.doris.qe.AuditEventProcessor$Worker.run(AuditEventProcessor.java:120)
at java.base/java.lang.Thread.run(Thread.java:833)
```
## Proposed changes
Issue Number: close #xxx
<!--Describe your changes.-->diff --git a/fe/fe-core/src/main/java/org/apache/doris/plugin/PluginMgr.java b/fe/fe-core/src/main/java/org/apache/doris/plugin/PluginMgr.java
index ea69b24..daf93f4 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/plugin/PluginMgr.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/plugin/PluginMgr.java
@@ -293,6 +293,10 @@
m.values().forEach(d -> {
if (d.getStatus() == PluginStatus.INSTALLED) {
+ if (d.getPlugin() == null) {
+ LOG.warn("PluginLoader({}) status is INSTALLED, but plugin is null", d);
+ return;
+ }
l.add(d.getPlugin());
}
});