`move tarp` results in error that hides flathead screwdriver

[pahp]

The Unused Office
This room is a small office, there is a wooden desk devoid of any identifying objects. One of the ceiling panels seems to be missing in here. Along the east wall there is a tarp laying on the floor, partially laying against the wall. There are 2 cans of paint here. The east wall seems to be still unpainted.

You can see a Tarp here.

> move tarp

[** Programming error: tried to test "has" or "hasnt" of nothing **]

[** Programming error: nothing (object number 0)  has no property before to send message **]

[pahp]

More weirdness. Here's what happens if you take the tarp:

> take tarp
As you fold up and take the tarp you notice underneath it there was a flathead screwdriver!
> l
The Unused Office
This room is a small office, there is a wooden desk devoid of any identifying objects. One of the ceiling panels seems to be missing in here. Along the east wall there is a tarp laying on the floor, partially laying against the wall. There are 2 cans of paint here. The east wall seems to be still unpainted.

You can see a Flathead here.

Here's what happens if you move the tarp:

> move tarp

[** Programming error: tried to test "has" or "hasnt" of nothing **]

[** Programming error: nothing (object number 0)  has no property before to send message **]

> l
The Unused Office
This room is a small office, there is a wooden desk devoid of any identifying objects. One of the ceiling panels seems to be missing in here. Along the east wall there is a tarp laying on the floor, partially laying against the wall. There are 2 cans of paint here. The east wall seems to be still unpainted.

>

The flathead screwdriver is not visible... but it is still there:

> take flathead
Taken.

[The score has just gone up by 4 points.]

[pahp]

Anyway, if someone tries to move tarp it not only gives them a weird error, but it breaks the hinge pin puzzle.