我正在使用grails 2.4.2和postgresql和grails db-migration 1.4.0插件。每当我发出grails dbm-update命令时，我都会得到以下异常，从而导致表创建失败：
Starting dbm-update for database user @ jdbc:postgresql://localhost:5432/mydb
liquibase.exception.LockException: liquibase.exception.DatabaseException: Empty result set, expected one row
at liquibase.lockservice.LockService.acquireLock(LockService.java:121)
at liquibase.lockservice.LockService.waitForLock(LockService.java:61)
at liquibase.Liquibase.update(Liquibase.java:102)
at DbmUpdate$_run_closure1_closure2.doCall(DbmUpdate:26)
at DbmUpdate$_run_closure2_closure11.doCall(DbmUpdate:59)
at grails.plugin.databasemigration.MigrationUtils.executeInSession(MigrationUtils.groovy:133)
at DbmUpdate$_run_closure2.doCall(DbmUpdate:51)
at DbmUpdate$_run_closure1.doCall(DbmUpdate:25)
Caused by: liquibase.exception.DatabaseException: Empty result set, expected one row
at liquibase.util.JdbcUtils.requiredSingleResult(JdbcUtils.java:124)
at liquibase.executor.jvm.JdbcExecutor.queryForObject(JdbcExecutor.java:159)
at liquibase.executor.jvm.JdbcExecutor.queryForObject(JdbcExecutor.java:167)
at liquibase.executor.jvm.JdbcExecutor.queryForObject(JdbcExecutor.java:163)
at liquibase.lockservice.LockService.acquireLock(LockService.java:96)
... 7 more
任何帮助将不胜感激。