Building multiple matrix builds (of one job) at once results in the following exception from the p4 plugin.

The job is configured as:
Multi-configuration project
Execute concurrent builds if necessary: true
p4 scm with a Manual workspace (viewname: "jenkins-${NODE_NAME}-${JOB_NAME}", workspace: "//depot/tool/... //jenkins-${NODE_NAME}-${JOB_NAME}/...")
User-defined Axis Name: "FOO" with Values "bar baz"
And a single build step executing a Windows batch command: "ping -n 10 127.0.0.1 >nul" to sleep for 10 seconds.

Trigger the same job at least twice in quick succession. The first succeeds but the subsequent ones get the above exception.

It appears to be a problem when the matrix per-configuration build uses the same node as the flyweight job. This is reproducible with a system with 1 executor on master.

Building on master in workspace C:\jenkins\jobs\matrix_p4_multiple_executions\ws@2\FOO\bar
FATAL: 1
java.lang.ArrayIndexOutOfBoundsException: 1
at org.jenkinsci.plugins.p4.tasks.AbstractTask.setEnvironment(AbstractTask.java:108)
at org.jenkinsci.plugins.p4.PerforceScm.checkout(PerforceScm.java:312)
at hudson.scm.SCM.checkout(SCM.java:485)
at hudson.model.AbstractProject.checkout(AbstractProject.java:1269)
at hudson.model.AbstractBuild$AbstractBuildExecution.defaultCheckout(AbstractBuild.java:607)
at jenkins.scm.SCMCheckoutStrategy.checkout(SCMCheckoutStrategy.java:86)
at hudson.model.AbstractBuild$AbstractBuildExecution.run(AbstractBuild.java:529)
at hudson.model.Run.execute(Run.java:1738)
at hudson.matrix.MatrixRun.run(MatrixRun.java:146)
at hudson.model.ResourceController.execute(ResourceController.java:98)
at hudson.model.Executor.run(Executor.java:410)