public void setNull(int colIndex) {
		dirty = true;
		Field f = fieldValues[colIndex];
		if (f.isVariableLength()) {
			invalidateLength();
		}
		f.setNull();
	}
Set the field to a null state.  For a non-sparse fixed-length column field this will
set the value to zero and the null state will not be persisted when stored.
@param colIndex field index
@throws IndexOutOfBoundsException if invalid columnIndex is specified
Ghidra/Framework/DB/src/main/java/db/DBRecord.java