Fix for Mantis #26180. Accept undefineddef as first parameter type of an Assert if it is used inside a generic.

ninl.pas, tinlinenode.pass_typecheck:
  * if the first parameter of an Assert is a undefineddef node then accept it as well if the node is part of a generic function/method

+ added test

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@27875 3ad0048d-3df7-0310-abae-a5850022a9f2