eldoc error: (wrong-type-argument stringp nil) - when cursor is around url

[vibrys]

Hi.
I'm running latest spacemacs devel + latest ein package update (ein-20230622.1757).

Complete backtrace looks like following:

Debugger entered--Lisp error: (wrong-type-argument stringp nil)
  propertize(nil face ein:markdown-url-face)
  ein:markdown-eldoc-function()
  apply(ein:markdown-eldoc-function nil)
  #f(advice-wrapper :before-until #f(compiled-function (&rest args) #<bytecode -0x1d35e848ea146836>) ein:markdown-eldoc-function)()
  eldoc--invoke-strategy(nil)
  eldoc-print-current-symbol-info()
  #f(compiled-function () #<bytecode -0x85c003cd0c4ae6a>)()
  apply(#f(compiled-function () #<bytecode -0x85c003cd0c4ae6a>) nil)
  timer-event-handler([t 0 0 500000 nil #f(compiled-function () #<bytecode -0x85c003cd0c4ae6a>) nil idle 0 nil])

please help