bug#72370: srfi-64: test-apply requires at least one specifier

Hello,

I think I found a bug in (srfi srfi-64) module shipped with GNU Guile.

The specification says the following regarding the test-apply:

> If one or more specifiers are listed then only tests matching the specifiers
> are executed.

That implies that specifiers are optional and the following code should work:

    (use-modules (srfi srfi-64))
    (test-apply (λ () #t))

However it does not:

    Backtrace:
    In ice-9/boot-9.scm:
      1752:10  8 (with-exception-handler _ _ #:unwind? _ #:unwind-for-type _)
    In unknown file:
               7 (apply-smob/0 #<thunk 7fdf6ecc4300>)
    In ice-9/boot-9.scm:
        724:2  6 (call-with-prompt _ _ #<procedure default-prompt-handler (k proc)>)
    In ice-9/eval.scm:
        619:8  5 (_ #(#(#<directory (guile-user) 7fdf6ecc7c80>)))
    In ice-9/boot-9.scm:
       2836:4  4 (save-module-excursion _)
      4388:12  3 (_)
    In srfi/srfi-64/testing.scm:
       947:34  2 (test-apply #<procedure 7fdf63956108 at /home/wolf/src/guile-wolfsden/tests/s…>)
       938:47  1 (test-apply #<procedure 7fdf63956108 at /home/wolf/src/guile-wolfsden/test…> . _)
    In unknown file:
               0 (reverse #t)

    ERROR: In procedure reverse:
    In procedure reverse: Wrong type argument in position 1: #t

Have a nice day
Tomas Volf