#65 SOAPParameter::IsNull() returns false despite nil="true"

[Peter Feltham]

There is a small bug in SOAPParameterHandler.cpp
when receiving a nil parameter.
The nil="true" attribute is received and stored correctly,
which would cause IsNull() to return true as expected.
However, in the endElement() function, the element
contents (which is an empty string) is assigned to the
SOAPParameter object and SetNull(false) is called,
clobbering the nil="true" attribute.
It seems to me that this endElement() processing
should not occur if the nil attribute is true, so to correct
this behaviour I have added a check for IsNull() in the
attached patch.

[Peter Feltham]

diff patch for SOAPParameterHandler.cpp to fix nil handling