does Gliese 445 pose any threat to earth when it passes close to our solar system?

It's not projected to get close enough to matter.

It will only get to just over 3 light years from our solar system, not close enough to affect even the Oort Cloud.

Nope, too far away.

The few remnants of Homo sapien who might just happen to still be around at the time might notice some pretty comets in the sky, but more than likely the fauna of the time won't notice or care.

I might be a bit more exciting in a few thousand years time

If it affects the orbits of objects in the Oort Cloud those effects wouldn't be noticed for thousands of years and it could take millions of years for the inner solar system to be affected. Take the comet ISON as an example it made a million year journey to the sun and it had no effect on earth.

It won't be close enough to pose any threat to our solar system at all. It will get less than 4 light years making it our suns closest neighbor. Maybe of good interest to back yard radio observers.

Well, not for tens of thousands of years, at least.

So far as its trajectory has been projected, in about 40,000 years, it could be close enough to gravitationally interact with some comets in the outer Oort Cloud. But it won't be close enough to pose any direct threat to Earth.