NumberParser::parseUnsigned should not parse negative numbers

The function should abort if a negative number (e.g. "-123") is passed as input

Foundation/testsuite/src/NumberParserTest.cpp

@@ -272,6 +272,12 @@ void NumberParserTest::testParseError()
 		failmsg("must throw SyntaxException");
 	} catch (SyntaxException&) { }
 
+	try
+	{
+		NumberParser::parseUnsigned("-123");
+		failmsg("must throw SyntaxException");
+	} catch (SyntaxException&) { }
+
 	try
 	{
 		NumberParser::parseHex("z23");