Fix split filter for php >=8.0 in case of empty separator (#213)

Co-authored-by: pavlikovsky <[email protected]>

Author: oleksii-pavlikovskii-eleks-com

src/Liquid/StandardFilters.php

@@ -621,6 +621,10 @@ public static function split($input, $pattern)
 			return [];
 		}
 
+		if ($pattern === '') {
+			return mb_str_split($input);
+		}
+
 		return explode($pattern, $input);
 	}
 

tests/Liquid/StandardFiltersTest.php

@@ -881,6 +881,21 @@ public function testSplit()
 				array('123', '123', '123'),
 				'0'
 			),
+			array(
+				'phrase',
+				array('p', 'h', 'r', 'a', 's', 'e'),
+				''
+			),
+			array(
+				'phrase',
+				array('phrase'),
+				null
+			),
+			array(
+				'123 123 123',
+				array('123', '123', '123'),
+				' '
+			),
 		);
 
 		foreach ($data as $item) {