Fixed obvious nullpointer bug in tixiGetTextAttribute.
Fixed obvious nullpointer bug in tixiGetTextAttribute.

DLR-SC/tixi,melven/tixi,DLR-SC/tixi,melven/tixi,melven/tixi,melven/tixi,DLR-SC/tixi,DLR-SC/tixi,DLR-SC/tixi,melven/tixi