Move directory on click into directory tree

Hey there,

I've been using PHPStorm for a week or two in order to replace my Zend Studio (good choice so far... :-) ).
However, every few times I click into the file tree on the left to focus the panel, I move the cursor a little too much and thus be prompted if I want to move the directory.
This is quite annoying and I guess I can't be the only one experiencing this.

In my opinion, PHPStorm shouldn't ask me if I want to move the directory when I accidentally drag'n'drop it (onto itself).

Is there a way to disable this behavior?

Greetings from Germany / Koblenz,
Daniel