flycheck-haskell fails to initialize when you have a cabal.config without 'with-compiler'

[nkpart]

I have projects with cabal.config files, that only specify constraints. In the latest version of flycheck-haskell, it fails to initialize while looking for with-compiler.

Debugger entered--Lisp error: (wrong-type-argument stringp nil)
  substring-no-properties(nil)
  flycheck-haskell-get-config-value(with-compiler)
  mapcar(flycheck-haskell-get-config-value (with-compiler))
  flycheck-haskell-parse-config-file((with-compiler) "/Users/nkpart/p/vlc/dredd/dredd/cabal.config")
  flycheck-haskell-get-cabal-config()
  flycheck-haskell-configure()
  run-hooks(flycheck-mode-hook flycheck-mode-on-hook)
  flycheck-mode()
  run-hooks(change-major-mode-after-body-hook prog-mode-hook haskell-mode-hook)
  apply(run-hooks (change-major-mode-after-body-hook prog-mode-hook haskell-mode-hook))
  run-mode-hooks(haskell-mode-hook)
  haskell-mode()
  set-auto-mode-0(haskell-mode nil)
  set-auto-mode()
  normal-mode()
  call-interactively(normal-mode record nil)
  command-execute(normal-mode record)
  helm-M-x(nil "normal-mode")
  call-interactively(helm-M-x nil nil)
  command-execute(helm-M-x)

[swsnr]

@nkpart Fixed, and released as 0.7.2 on MELPA Stable. Thanks for reporting this issue.