Prevent from more than one location pin appearing

[SarahHCode]

Describe the bug
Sometimes, more than one location pin appears... maybe it's because the location pin layer function re-runs (map re-renders or something?).

Solution: Remove existing location pin layer each time its function runs.

To Reproduce
Steps to reproduce the behavior:

1. Go to map.
2. See error sometimes.

Expected behavior
One location pin only should be present.

Screenshots

Smartphone (please complete the following information):

• Device: iPhone