fix: hide network picker back button when network is unselected

[micaelae]

Description

This hides the network picker's back button when there's no selected network. Currently this causes the dest network picker to navigate to the src asset picker

Related issues

Fixes: https://consensyssoftware.atlassian.net/browse/MMS-1852

Manual testing steps

1. Load bridge page
2. Open dest asset picker
3. Verify that back button is not visible

Screenshots/Recordings

Before

Screen.Recording.2025-01-21.at.12.26.52.PM.mov

After

Screen.Recording.2025-01-21.at.12.27.33.PM.mov

Pre-merge author checklist

• I've followed MetaMask Contributor Docs and MetaMask Extension Coding Standards.
• I've completed the PR template to the best of my ability
• I’ve included tests if applicable
• I’ve documented my code using JSDoc format if applicable
• I’ve applied the right labels on the PR (see labeling guidelines). Not required for external contributors.

Pre-merge reviewer checklist

• I've manually tested the PR (e.g. pull and build branch, run the app, test code being changed).
• I confirm that this PR addresses all acceptance criteria described in the ticket it closes and includes the necessary testing evidence such as recordings and or screenshots.

[metamaskbot]

Builds ready [d1b7579]

• builds: chrome, firefox
• builds (flask): chrome, firefox
• builds (MMI): chrome
• builds (test): chrome, firefox
• builds (test-flask): chrome, firefox
• build viz: Build System
• mv3: Bundle Size Stats
• mv2: E2e Actions Stats
• storybook: Storybook
• typescript migration: Dashboard
• all artifacts
• bundle viz:

  • background: 0, 1, 2, 3, 4, 5, 6, 7
  • common: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12
  • ui: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13
  • content-script: 0
  • offscreen: 0

Page Load Metrics (1513 ± 44 ms)

Platform	Page	Metric	Min (ms)	Max (ms)	Average (ms)	StandardDeviation (ms)	MarginOfError (ms)
Chrome	Home	firstPaint	1385	1689	1515	91	44
		domContentLoaded	1378	1674	1490	88	42
		load	1387	1687	1513	91	44
		domInteractive	23	90	38	19	9
		backgroundConnect	5	83	23	22	10
		firstReactRender	15	102	57	30	14
		getState	5	81	17	23	11
		initialActions	0	1	0	0	0
		loadScripts	993	1297	1111	83	40
		setupStore	5	86	10	17	8
		uiStartup	1550	2280	1847	205	98

Bundle size diffs

• background: 0 Bytes (0.00%)
• ui: 12 Bytes (0.00%)
• common: 0 Bytes (0.00%)

[metamaskbot]

Builds ready [a4e168e]

• builds: chrome, firefox
• builds (flask): chrome, firefox
• builds (MMI): chrome
• builds (test): chrome, firefox
• builds (test-flask): chrome, firefox
• build viz: Build System
• mv3: Bundle Size Stats
• mv2: E2e Actions Stats
• storybook: Storybook
• typescript migration: Dashboard
• all artifacts
• bundle viz:

  • background: 0, 1, 2, 3, 4, 5, 6, 7
  • common: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13
  • ui: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13
  • content-script: 0
  • offscreen: 0

Page Load Metrics (1844 ± 157 ms)

Platform	Page	Metric	Min (ms)	Max (ms)	Average (ms)	StandardDeviation (ms)	MarginOfError (ms)
Chrome	Home	firstPaint	318	2605	1782	467	224
		domContentLoaded	1460	2542	1822	322	155
		load	1471	2594	1844	326	157
		domInteractive	22	100	51	24	12
		backgroundConnect	9	85	23	19	9
		firstReactRender	16	78	40	23	11
		getState	5	62	24	20	9
		initialActions	0	0	0	0	0
		loadScripts	1079	2038	1371	280	135
		setupStore	6	71	17	20	9
		uiStartup	1644	2929	2095	363	174

Bundle size diffs

• background: 0 Bytes (0.00%)
• ui: 12 Bytes (0.00%)
• common: 0 Bytes (0.00%)

[metamaskbot]

Builds ready [76a5638]

• builds: chrome, firefox
• builds (flask): chrome, firefox
• builds (MMI): chrome
• builds (test): chrome, firefox
• builds (test-flask): chrome, firefox
• build viz: Build System
• mv3: Bundle Size Stats
• mv2: E2e Actions Stats
• storybook: Storybook
• typescript migration: Dashboard
• all artifacts
• bundle viz:

  • background: 0, 1, 2, 3, 4, 5, 6, 7
  • common: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13
  • ui: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13
  • content-script: 0
  • offscreen: 0

Page Load Metrics (1627 ± 30 ms)

Platform	Page	Metric	Min (ms)	Max (ms)	Average (ms)	StandardDeviation (ms)	MarginOfError (ms)
Chrome	Home	firstPaint	1485	1753	1627	63	30
		domContentLoaded	1475	1738	1607	58	28
		load	1486	1753	1627	62	30
		domInteractive	24	96	43	21	10
		backgroundConnect	6	54	24	15	7
		firstReactRender	15	96	38	27	13
		getState	4	59	18	20	10
		initialActions	0	1	0	0	0
		loadScripts	1083	1300	1193	51	24
		setupStore	6	47	10	9	4
		uiStartup	1726	2361	1892	139	67

Bundle size diffs

• background: 0 Bytes (0.00%)
• ui: 12 Bytes (0.00%)
• common: 0 Bytes (0.00%)