Union the rectangle with another rectangle.
This rectangle becomes the smallest rectangle that encloses both
Rectangles with no area will, by default, be treated as being
empty. A union of a non-empty rectangle with an empty rectangle
always results in the output being set to the non-empty rectangle
value. If both rectangles are empty this rectangle will be left
If the noAreaIsEmpty parameter is set to false then rectangles
with no area will be treated as points and the output union will
include that point.