Define the $php, $css and, $other variables as an array to avoi…

…d a PHP Notice.

checkbase.php

@@ -47,6 +47,7 @@ function run_themechecks_against_theme( $theme, $theme_slug ) {
 		true /* include parent theme files */
 	);
 
+	$php = $css = $other = array();
 	foreach ( $files as $filename ) {
 		if ( substr( $filename, -4 ) === '.php' ) {
 			$php[ $filename ] = file_get_contents( $filename );