fixed bug with substring on ZString.

ZString.cpp

@@ -252,9 +252,8 @@ namespace coreutils {
       char *startChar = data + start;
       char *endChar = startChar + len;
       char newlen = endChar > end ? endChar - end: len;
-      if(startChar < end) {
-	 return ZString(startChar, newlen);
-      }
+      if(startChar < end) 
+	return ZString(startChar, newlen);
       return ZString();
    }