!4010 [bugfix] 修复WLMArbiter线程如果比PM线程更早收到退出消息而触发PANIC导致coredump问题

Merge pull request !4010 from 周斌/wlmarbiter

src/common/backend/utils/error/elog.cpp

@@ -287,7 +287,7 @@ bool errstart(int elevel, const char* filename, int lineno, const char* funcname
                  * during which panic is not expected.
                  */
                 if (AmCheckpointerProcess() || AmBackgroundWriterProcess() || AmWalReceiverWriterProcess() ||
-                    AmDataReceiverWriterProcess())
+                    AmDataReceiverWriterProcess() || AmWLMArbiterProcess())
                     elevel = FATAL;
                 else
                     elevel = PANIC;