fix(tasks): newly assigned None in registry

[SaidBySolo]

How to reproduce?

from sanic import Sanic
from asyncio import sleep, create_task

app = Sanic(__name__)


async def task():
    while True:
        await sleep(10)


@app.before_server_start
async def dummy_start(app, _):
    app.add_task(create_task(task()), name="Dummy")


@app.before_server_stop
async def dummy_stop(app, _):
    # Raise RuntimeError: dictionary changed size during iteration
    app.purge_tasks()


app.run()

sanic/sanic/app.py

Lines 1273 to 1274 in b8d9914

	name = task.get_name()
	self._task_registry[name] = None

If a name is not registered during create_task, the following name is obtained as Task-1, so the error that occurred because it is newly assigned has been resolved.

[codecov]

Codecov Report

Merging #2381 (9476754) into main (88bc6d8) will increase coverage by 0.017%.
The diff coverage is 100.000%.

@@              Coverage Diff              @@
##              main     #2381       +/-   ##
=============================================
+ Coverage   87.090%   87.107%   +0.017%     
=============================================
  Files           60        60               
  Lines         5004      5003        -1     
  Branches       905       905               
=============================================
  Hits          4358      4358               
  Misses         472       472               
+ Partials       174       173        -1     

Impacted Files	Coverage Δ
sanic/app.py	89.668% <100.000%> (+0.174%)	⬆️

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[ahopkins]

Can you add a unit test?

[SaidBySolo]

@ahopkins

All tests passed!

I'm not sure if the test I wrote is correct.