There should be some kind of check to see if the enviroment variable 
ALLOCATION_JAR has been set.

For example,
if (type == MeasurementType.INSTANCE || type == MeasurementType.MEMORY) {
      String allocationJarFile = System.getenv("ALLOCATION_JAR");
      if (allocationJarFile == null) {
        throw new Error("Enviroment variable ALLOCATION_JAR must be set before --measureMemory option can be used")
      }
}

Current version just fails with

> Failed to execute java -javaagent:null -cp  ....
> Error occurred during initialization of VM
> agent library failed to init: instrument
> Error opening zip file or JAR manifest missing : null

If ALLOCATION_JAR has not been specified. 

Also there is no mention in any of Calipers documentation about the need for 
settings this variable