Slow portfolio balance calls can cause balance to show incorrectly

[kylehickinson]

If you switch to the same network multiple times (which will cause balance calls to execute) there is a chance for the balance calls to double-up as the assets for that network will be the same. The balances will then add up incorrectly.

Most likely there are race conditions between fetching balances and prices where userVisibleAssets is already set with some balances and thus its adding balances to a state that isn't currently 0.

[Pavneet-Sing]

After further usage:

• It keeps on adding the original amount to the balance
• The incorrect balance remains there after lock/unlock

Possible quick fixes:

• Don't do anything if the newly selected network is same as the previous one
• Show loading to block the selection until the balance is refreshed

[kjozwiak]

Verification PASSED on iPhone 10 running 15.4.1 using 1.37 (22.4.6.8)

Went through the STR/Cases outlined via #5098 (comment) and ensured that the current balance wasn't appearing as $0.00 or was exceeding what's actually present.

Example	Example

---

Verification PASSED on iPhone 6+ running 14.6 using 1.37 (22.4.6.8)

Went through the STR/Cases outlined via #5098 (comment) and ensured that the current balance wasn't appearing as $0.00 or was exceeding what's actually present.

Example	Example