fix #117
fix #117

Segfault was occuring in the following context:
- Calling OCI_BindObject() with valid OCI_Object
- Binding direction is both IN and OUT
- Calling OCI_BindSetNull() for the given object bind
- Calling OCI_Execute()
- Calling OCI_StatementFree()

Segfault occurred in OCI_StatementFree()

vrogier/ocilib,vrogier/ocilib,ljx0305/ocilib,ljx0305/ocilib,vrogier/ocilib,vrogier/ocilib,ljx0305/ocilib