Fixing tag generation for Html::script() and Html::css() when using 'fullBase' => true.

Changing values on array_diff_key() from empty ('') to null as they have no consequences and offer better readability.
Merge pull request #1207 from renansaddam/supportFullBaseOnScriptAndCss

Fix missing support for fullBase in script() & css()

HtmlHelper::script(), HtmlHelper::css() did not have support for fullBase
added when it was added to image(). Fix that omission.