npe from alerting expression suggestor

[FrankChen021]

2025-08-26 10:46:27.485 ERROR 1 --- [nio-9897-exec-1] o.b.s.s.e.GlobalExceptionHandler         : [bTxId: 0198e4450d8c8e3cf374523eb5ba9403, bSpanId: 90b80bea002a87ed, bMode: T] Unexpected error

java.lang.NullPointerException: Cannot invoke "org.antlr.v4.runtime.Token.getType()" because "newToken" is null
	at org.bithon.server.commons.autocomplete.AutoSuggester.isValid(AutoSuggester.java:359) ~[server-commons-11.0.0-RELEASE.jar!/:na]
	at org.bithon.server.commons.autocomplete.AutoSuggester.validateSuggestions(AutoSuggester.java:317) ~[server-commons-11.0.0-RELEASE.jar!/:na]
	at org.bithon.server.commons.autocomplete.AutoSuggester.suggestNextTokensForParserState(AutoSuggester.java:242) ~[server-commons-11.0.0-RELEASE.jar!/:na]
	at org.bithon.server.commons.autocomplete.AutoSuggester.parseAndCollectTokenSuggestions(AutoSuggester.java:160) ~[server-commons-11.0.0-RELEASE.jar!/:na]
	at org.bithon.server.commons.autocomplete.AutoSuggester.suggest(AutoSuggester.java:100) ~[server-commons-11.0.0-RELEASE.jar!/:na]
	at org.bithon.server.commons.autocomplete.AutoSuggester.suggest(AutoSuggester.java:85) ~[server-commons-11.0.0-RELEASE.jar!/:na]
	at org.bithon.server.alerting.manager.biz.AlertExpressionSuggester.suggest(AlertExpressionSuggester.java:288) ~[server-alerting-manager-11.0.0-RELEASE.jar!/:na]
	at org.bithon.server.alerting.manager.api.AlertQueryApi.suggestAlertExpression(AlertQueryApi.java:137) ~[server-alerting-manager-11.0.0-RELEASE.jar!/:na]
	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103) ~[na:na]