Replace x() by isset(), !empty() or defaults()

- Remove extraneous parentheses around empty() calls
- Remove duplicate calls to intval(), count() or strlen() after empty()
- Replace ternary operators outputting binary value with empty() return value
- Rewrite defaults() without x()

mod/home.php

@@ -29,10 +29,10 @@ function home_init(App $a) {
 if(! function_exists('home_content')) {
 function home_content(App $a) {
 
-	if (x($_SESSION,'theme')) {
+	if (!empty($_SESSION['theme'])) {
 		unset($_SESSION['theme']);
 	}
-	if (x($_SESSION,'mobile-theme')) {
+	if (!empty($_SESSION['mobile-theme'])) {
 		unset($_SESSION['mobile-theme']);
 	}