Check four byte prefix object is empty

[tmashuang]

Fixes #8835

In cases where the initial registry failed to load, and the sig is set to {} on this line:

metamask-extension/ui/app/helpers/utils/transactions.util.js

Line 78 in e85b162

return {}

this proceeds to set the four byte method to {} in knownMethodData.

Additionally check if the method four byte prefix object is empty to proceed call getMethodDataAsync again.

I could only reproduce by intentionally failing the method registry lookup and found this solution. I could not find an instance where the registry consistently failed to lookup even on slow/throttled/high latency networks.

[metamaskbot]

Builds ready [05ecda8]

• builds: chrome, firefox, opera
• bundle viz: background, ui, inpage, contentscript, ui-libs, bg-libs, phishing-detect
• dep viz: background
• all artifacts

Page Load Metrics (716 ± 43 ms)

Platform	Page	Metric	Min (ms)	Max (ms)	Average (ms)	StandardDeviation (ms)	MarginOfError (ms)
Chrome	Home	firstPaint	34	94	59	24	12
		domContentLoaded	398	836	714	90	43
		load	400	838	716	90	43
		domInteractive	398	836	714	90	43

[brad-decker]

This change makes sense to me, but I don't have a lot of context with this API so I'm not going to mark approved. LGTM though!

[Gudahtt]

Interesting. So the blank entry gets cached and referred to later, preventing additional lookup attempts.

This would all probably be a lot simpler if that {} was never returned from getMethodDataAsync, but we can clean that up later. Changing that would be a bit more difficult.

LGTM!