VMPC error on C-x m

Doing C-x m while inside a random buffer produced this error message:

Debugger entered--Lisp error: (wrong-type-argument arrayp nil)
  vmpc-folder-account-match("vmrocks")
  (and (vmpc-folder-account-match "vmrocks"))
  (progn (and (vmpc-folder-account-match "vmrocks")))
  eval((progn (and (vmpc-folder-account-match "vmrocks"))))
  mapc(...)
  vmpc-build-true-conditions-list()
  vm-mail()
  call-interactively(vm-mail nil nil)