"Sprint id must be a number error occurred" when bulk change sprint

An error occurred whilst rendering this message. Please contact the administrators, and inform them of this bug. Details: ------- org.apache.velocity.exception.MethodInvocationException: Invocation of method 'convertEditValueToObjects' in class com.atlassian.greenhopper.customfield.sprint.SprintCFType threw exception com.atlassian.jira.issue.customfields.impl.FieldValidationException: Sprint id must be a number: Sprint 2 at com.pyxis.greenhopper.jira:gh-sprint//templates/greenhopper/jira/customfield/sprint/edit-sprint.vm[line 3, column 57] at org.apache.velocity.runtime.parser.node.ASTMethod.handleInvocationException(ASTMethod.java:337) at org.apache.velocity.runtime.parser.node.ASTMethod.execute(ASTMethod.java:284) at org.apache.velocity.runtime.parser.node.ASTReference.execute(ASTReference.java:262) at org.apache.velocity.runtime.parser.node.ASTReference.value(ASTReference.java:507) at org.apache.velocity.runtime.parser.node.ASTExpression.value(ASTExpression.java:71) at org.apache.velocity.runtime.parser.node.ASTSetDirective.render(ASTSetDirective.java:142) at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:336) at org.apache.velocity.Template.merge(Template.java:328) at org.apache.velocity.Template.merge(Template.java:235) at org.apache.velocity.app.VelocityEngine.mergeTemplate(VelocityEngine.java:381) at com.atlassian.velocity.DefaultVelocityManager.writeEncodedBodyImpl(DefaultVelocityManager.java:117) at com.atlassian.velocity.DefaultVelocityManager.writeEncodedBody(DefaultVelocityManager.java:97) at com.atlassian.jira.template.velocity.DefaultVelocityTemplatingEngine$DefaultRenderRequest.toWriterImpl(DefaultVelocityTemplatingEngine.java:146) at com.atlassian.jira.template.velocity.DefaultVelocityTemplatingEngine$DefaultRenderRequest.asHtml(DefaultVelocityTemplatingEngine.java:134) at com.atlassian.jira.plugin.AbstractJiraModuleDescriptor.writeHtml(AbstractJiraModuleDescriptor.java:133)
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