Suppose you have matrix project called "configuredmatrix" with single dimension called "config" having two possible values "A" and "B".
Create a new multijob instance called "multijobA" add new MultiJob phase
In the job fields start typing "configurematrix";
Note that UI will offer three options: "configurematrix", "configurematrix/config=A" and "configurematrix/config=B"
Choose "configurematrix/config=A"
Save your multijob project
Run your multijob project and check the console output for following:

Starting build job configurematrix/config=A.
java.lang.NullPointerException
...
Finished: SUCCESS

MultijobA would be marked as successful while it clearly had an exception and configurematrix job instance had never run.

If UI offers the option of specific matrix configuration to chose (I'm not sure which plugin implements that) then user should be able to use it without errors.

As the workaround we use "configurematrix" as the executed job and restrict matrix execution to a subset with following filter: config=="A"