Allow overwrite value by None if already defined

I have 2 dotenv files:

Scenario1:
/var/www/flask/.envRoot <---- myVar="foo"
and
/home/userA/.envA <----------- myVar="bar"

load_dotenv(dotenv_path='/var/www/flask/.envRoot',override=True)
os.getenv('myVar')   #  foo
load_dotenv(dotenv_path='/home/userA/.envA',override=True)
os.getenv('myVar')   #  bar

Scenario2:
/var/www/flask/.envRoot <---- myVar="foo"
and
/home/userA/.envA <----------- myVar not defined

load_dotenv(dotenv_path='/var/www/flask/.envRoot',override=True)
os.getenv('myVar')   #  foo
load_dotenv(dotenv_path='/home/userA/.envA',override=True)
os.getenv('myVar')   #  foo

Scenario1 work as spected, but Scenario2 should return None if do not exist on .envA because i explicitly indicate the file to look at. But this do not happen if the key exist e.g: myVar=, only if not defined.

Start at the load_dotenv entry point and trace how a later file is handled when myVar is absent versus explicitly set to an empty value. Compare the two scenarios in the issue, then verify that loading .envA removes the earlier value and returns None when myVar is not defined there.