Resolves two long standing errors in 'cdk-extra'. The method should throw an exception when one tries to attach to an invalid atom number (e.g. 7-chlorohexane). The existing error was using the ParseException constructor incorrectly and thus would throw an error. The constructor is for generating error messages to do with syntax. As this is a semantic error the constructor did not function as intended. Simply replacing the use of this constructor with a normal error message resolves the issue.

Change-Id: I896e3a3d07322e0a98f317cb331f4ebfe66f8e15
Signed-off-by: Egon Willighagen <egonw@users.sourceforge.net>