Database presets will not import when they are contained in a subfolder.

Steps to reproduce: (Using Moodle 1.9 + Build 20080410)

1. In the files area create a folder called "test"
2. upload the preset to the newly created "test" folder
(I had used the buzz preset see http://moodle.org/mod/forum/discuss.php?d=84050&parent=371801)

3. Create a new database activity (I had only set the name and introduction, the rest of the settings were left as the defaults)
4. Import the buzz preset from the import tab.
(See attached screenshot1.png)

5. Moodle generates the following error: "Can't unzip file"
(See attached screenshot2.png)
This only occurs if the preset is contained in a sub folder. If the preset is contained in the root of the course files area it will unzip properly.

The problem seems be be with line 156 of mod/data/preset.php