Internal server error deleting a non-existing glossary entry

Description

Deleting an item in glossary that was already deleted should not cause an internal server error.

> ~/dev/zanata-platform/client/zanata-cli/target/appassembler/bin/zanata-cli -e glossary-delete --id 977
[INFO] Loading config from zanata.xml
[INFO] Loading user config from ~/.config/zanata.ini
[INFO] Error stacktraces are turned on.
[INFO] client API version: 4.0.0-SNAPSHOT, server API version: 4.0.0-SNAPSHOT
[INFO] Server: http://localhost:8180/
[INFO] Username: admin
[INFO] Entry id to delete: 977
[INFO] Delete entire glossary?: false
[ERROR] Execution failed:
javax.ws.rs.client.ResponseProcessingException: javax.ws.rs.ServerErrorException: operation to http://localhost:8180/rest/glossary/entries/977?qualifiedName=global%2Fdefault returned 500 (Internal Server Error)::<html><head><title>Error</title></head><body>Internal Server Error</body></html>
at org.jboss.resteasy.client.jaxrs.internal.ClientInvocation.invoke(ClientInvocation.java:455)
at org.jboss.resteasy.client.jaxrs.internal.ClientInvocationBuilder.delete(ClientInvocationBuilder.java:213)
at org.zanata.rest.client.GlossaryClient.delete(GlossaryClient.java:82)
at org.zanata.client.commands.glossary.delete.GlossaryDeleteCommand.run(GlossaryDeleteCommand.java:87)
at org.zanata.client.commands.ConfigurableCommand.runWithActions(ConfigurableCommand.java:110)
at org.zanata.client.commands.ArgsUtil.runCommand(ArgsUtil.java:48)
at org.zanata.client.ZanataClient.processArgs(ZanataClient.java:177)
at org.zanata.client.ZanataClient.main(ZanataClient.java:102)
Caused by: javax.ws.rs.ServerErrorException: operation to http://localhost:8180/rest/glossary/entries/977?qualifiedName=global%2Fdefault returned 500 (Internal Server Error)::<html><head><title>Error</title></head><body>Internal Server Error</body></html>
at org.zanata.rest.client.ResponseStatusFilter.filter(ResponseStatusFilter.java:89)
at org.jboss.resteasy.client.jaxrs.internal.ClientInvocation.invoke(ClientInvocation.java:447)
... 7 more