[configuration] PropertiesConfiguration doesn't throw exception when path is directory

When I use a string which is a directory to create a PropertiesConfiguration, no
exception is thrown. However, the configuration is unusable as it has no
properties.

For example, I do

<code>
PropertiesConfiguration temp =
new PropertiesConfiguration("c:/baddirectory");
</code>

I get the expected

<code>
org.apache.commons.configuration.ConfigurationException: Cannot locate
configuration source baddirectory
</code>

However, when I do

PropertiesConfiguration temp2 = new
PropertiesConfiguration("c:/windows");

I don't get any exception. The difference between "baddirectory" and "windows"
is that the former doesn't exist and the latter does.