Preserve gender of a destination symbol when assigning family member of unknown gender who's not in the pedigree yet

When dragging symbol of Unknown gender from "Family members not in pedigree" over the symbol with defined gender, preserve the known gender.

For example:

• open pedigree and create a simple family mother-father-child
• click on Add family member button -> a symbol of an unknown gender will be created in the "Family members not in pedigree" section
• drag the newly created patient over the father node
• father node will lose its gender ( it should not)