Event loading progress indicator goes wild when switching account while loading events

[TripleSpeeder]

Reproduce:

• Open "View Transfer Events"
• Select a token and account -> events start to get loaded
• While events are still loading, switch to a different account

=> Now events for two different token-account combinations are loading in parallel. This leads to the progress info going wild, as it jumps between the progress for both combinations.

The parallel loading itself is not an issue, but the UI should only show the progress of the currently selected combination.