Fixes an issue cancelling a permission request

[FrederikBolding]

Description

I introduced a bug in #22850 which can be reproduced by going to the test-dapp, starting a permission request flow, proceeding to the next screen and cancelling it again. This fixes the problem by guarding against permissions being null.

Manual testing steps

1. Go to the test-dapp
2. Connect
3. Click next
4. Click cancel
5. See that the extension does not crash

[metamaskbot]

Builds ready [a87e5ab]

• builds: chrome, firefox
• builds (beta): chrome
• builds (flask): chrome, firefox
• builds (MMI): chrome, firefox
• builds (test): chrome, firefox
• builds (test-flask): chrome, firefox
• build viz: Build System
• mv3: Background Module Init Stats
• mv3: UI Init Stats
• mv3: Module Load Stats
• mv3: Bundle Size Stats
• mv2: E2e Actions Stats
• code coverage: Report
• storybook: Storybook
• typescript migration: Dashboard
• all artifacts
• bundle viz:

  • background: 0, 1, 2, 3, 4
  • common: 0, 1, 2, 3, 4, 5, 6, 7
  • content-script: 0
  • contentscript: contentscript
  • disable-console: disable-console
  • policy-load: policy-load
  • sentry-install: sentry-install
  • ui: 0, 1, 10, 11, 2, 3, 4, 5, 6, 7, 8, 9

Page Load Metrics (1134 ± 57 ms)

Platform	Page	Metric	Min (ms)	Max (ms)	Average (ms)	StandardDeviation (ms)	MarginOfError (ms)
Chrome	Home	firstPaint	126	303	215	42	20
		domContentLoaded	11	127	50	36	17
		load	870	1324	1134	119	57
		domInteractive	11	127	50	36	17

Bundle size diffs

• background: 0 Bytes (0.00%)
• ui: 4 Bytes (0.00%)
• common: 0 Bytes (0.00%)