escaping backslash should be included in split items

lib/plugins/authplain/_test/escaping.test.php

@@ -97,7 +97,7 @@ class helper_plugin_authplain_escaping_test extends DokuWikiTest {
             $test_line = $userpass.$escaped.$other_user_data;
             $result = $this->auth->splitUserData($test_line);
 
-            $this->assertEquals($testname, $result[2]);
+            $this->assertEquals($escaped, $result[2]);
         }
     }
     

lib/plugins/authplain/auth.php

@@ -356,9 +356,12 @@ class auth_plugin_authplain extends DokuWiki_Auth_Plugin {
 
         $row = array();
         $piece = '';
-        for($i=0; $i<strlen($line); $i++){
+        $len = strlen($line);
+        for($i=0; $i<$len; $i++){
             if ($line[$i]=='\\'){
+                $piece .= $line[$i];
                 $i++;
+                if ($i>=$len) break;
             } else if ($line[$i]==':'){
                 $row[] = $piece;
                 $piece = '';