"bin/flink savepoint -d :savepointpath" cannot locate savepointpath arg

Hi there,

When I use "bin/flink savepoint -d :savepointpath" to dispose a savepoint, got following exceptions:
The program finished with the following exception:java.lang.NullPointerException: Missing required argument: savepoint path. Usage: bin/flink savepoint -d <savepoint-path>
at org.apache.flink.util.Preconditions.checkNotNull(Preconditions.java:76)
at org.apache.flink.client.cli.CliFrontend.disposeSavepoint(CliFrontend.java:785)
at org.apache.flink.client.cli.CliFrontend.lambda$savepoint$8(CliFrontend.java:723)
at org.apache.flink.client.cli.CliFrontend.runClusterAction(CliFrontend.java:1002)
at org.apache.flink.client.cli.CliFrontend.savepoint(CliFrontend.java:719)
at org.apache.flink.client.cli.CliFrontend.parseAndRun(CliFrontend.java:1072)
at org.apache.flink.client.cli.CliFrontend.lambda$main$10(CliFrontend.java:1132)
at java.base/java.security.AccessController.doPrivileged(Native Method)
at java.base/javax.security.auth.Subject.doAs(Subject.java:423)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1807)
at org.apache.flink.runtime.security.contexts.HadoopSecurityContext.runSecured(HadoopSecurityContext.java:41)
at org.apache.flink.client.cli.CliFrontend.main(CliFrontend.java:1132)
However, if I use "bin/flink savepoint -dispose :savepointpath", it works good.