Update NEXT-RNAi.pl

[pindao]

Perl v5.6.1 deprecated the defined function, and it returns the message below. The defined function is omitted to fix the error.

Can't use 'defined(%hash)' (Maybe you should just omit the defined()?) at
nextrnai/NEXT-RNAi.pl line 645 (#1)
(F) defined() is not usually right on hashes.

Although defined %hash is false on a plain not-yet-used hash, it
becomes true in several non-obvious circumstances, including iterators,
weak references, stash names, even remaining true after undef %hash.
These things make defined %hash fairly useless in practice, so it now
generates a fatal error.

If a check for non-empty is what you wanted then just put it in boolean
context (see "Scalar values" in perldata):

    if (%hash) {
       # not empty
    }

If you had defined %Foo::Bar::QUUX to check whether such a package
variable exists then that's never really been reliable, and isn't
a good way to enquire about the features of a package, or whether
it's loaded, etc.

Uncaught exception from user code:
Can't use 'defined(%hash)' (Maybe you should just omit the defined()?) at nextrnai/NEXT-RNAi.pl line 645.