Fix parsing empty files with mb off

Closes #100

Author: sabberworm

lib/Sabberworm/CSS/Parser.php

@@ -43,7 +43,11 @@ public function __construct($sText, Settings $oParserSettings = null) {
 		if ($this->oParserSettings->bMultibyteSupport) {
 			$this->aText = preg_split('//u', $sText, null, PREG_SPLIT_NO_EMPTY);
 		} else {
-			$this->aText = str_split($sText);
+			if($sText === '') {
+				$this->aText = array();
+			} else {
+				$this->aText = str_split($sText);
+			}
 		}
 		$this->blockRules = explode('/', AtRule::BLOCK_RULES);
 

tests/Sabberworm/CSS/ParserTest.php

@@ -377,9 +377,21 @@ function testComments() {
 		$this->assertSame($sExpected, $oDoc->render());
 	}
 
-	function parsedStructureForFile($sFileName) {
+  function testEmptyFile() {
+    $oDoc = $this->parsedStructureForFile('-empty', Settings::create()->withMultibyteSupport(true));
+		$sExpected = '';
+		$this->assertSame($sExpected, $oDoc->render());
+  }
+
+  function testEmptyFileMbOff() {
+    $oDoc = $this->parsedStructureForFile('-empty', Settings::create()->withMultibyteSupport(false));
+		$sExpected = '';
+		$this->assertSame($sExpected, $oDoc->render());
+  }
+
+	function parsedStructureForFile($sFileName, $oSettings = null) {
 		$sFile = dirname(__FILE__) . '/../../files' . DIRECTORY_SEPARATOR . "$sFileName.css";
-		$oParser = new Parser(file_get_contents($sFile));
+		$oParser = new Parser(file_get_contents($sFile), $oSettings);
 		return $oParser->parse();
 	}