Should allow preferences having empty default

Please,

consider the following snippet from plugin.xml

<platform name="ios"><preference name="VERSION" default="" /><framework src="Google-Mobile-Ads-SDK" type="podspec" spec="$VERSION" /></platform>

It would be useful if preferences having an empty default are considered valid instead of missing.

This new behavior lets you use a preference to specify a podspec version and if the preference has empty default, it means the latest version should be installed.

Today, there is no other way to do it unless CocoaPods changes podfile to let you specify something like +, * or latest to install the latest version of a podspec (instead of omitting the version at all).