Fix tests

Author: Vincent Wilms

tests/PureHDF.Tests/DumpFiles/data_default_fls_String[].dump

@@ -11,7 +11,7 @@ GROUP "/" {
       DATA {
       (0): "ABCDEF",
       (1): "\37777777703\37777777604\37777777703\37777777634\37777777703\37777777626",
-      (2): "123456", "1234\000\000", "\000\000\000\000\000\000"
+      (2): "123456", "1234", ""
       }
    }
 }