Fix EZP-22974: When I create a new Image I get Error: eZDir::recursiveDelete

Possible fix for

#### EZP-22974 - 22974: When I create a new Image I get Error: eZDir::recursiveDelete

If you create a new image, with page redirect enabled, you'll get the following error

```
Error: eZDir::recursiveDelete 	Jun 02 2014 15:13:44
The path: var/ezwebin_site/cache/template-block/subtree/1/cache is not a folder
```
I thought this was frowned upon in Engineering - i.e. it's recommended to fix the problem, not hide the symptom. So I would check "if ( !file_exists() ) break;" first (it works on both files and directories) and then do the if / else as it is here - without the '@'. But let's get a second voice from Engineering on that.