Failed to run query: Database is not registered

从第 175 行的 QueryServer2BackendManager.withDB 开始，跟踪使用新选定数据库时的查询服务器注册路径。通过选择一个数据库、运行快速查询并观察是否需要重启查询服务器来复现；完成标准是查询无需该重启即可运行。

Happens about half the time I select a new database, make a quick query and try to run it:

                              com.semmle.util.exception.UserError: Database is not registered: /private/tmp/db
                              	at com.semmle.cli2.execute.queryServer2.QueryServer2BackendManager.withDB(QueryServer2BackendManager.java:175)
                              	at com.semmle.cli2.execute.queryServer2.QueryServer2BackendManager.withDBShared(QueryServer2BackendManager.java:70)
                              	at com.semmle.cli2.execute.queryServer2.QueryServer2Command$Impl.lambda$runQuery$26(QueryServer2Command.java:580)
                              	at com.semmle.util.concurrent.FutureUtils.supplyCompose(FutureUtils.java:248)
                              	at com.semmle.cli2.execute.queryServer2.QueryServer2Command$Impl.lambda$runQuery$28(QueryServer2Command.java:560)
                              	at com.semmle.cli2.execute.queryServer2.QueryServer2Command$Impl.lambda$withProgressAndCancellation$15(QueryServer2Command.java:405)
                              	at com.semmle.util.concurrent.FutureUtils.supplyCompose(FutureUtils.java:248)
                              	at com.semmle.cli2.execute.queryServer2.QueryServer2Command$Impl.lambda$withProgressAndCancellation$16(QueryServer2Command.java:404)
                              	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
                              	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)

Restarting the query server always fixes the situation.