fix(linux/xdgportal): Additional error handling and minor code improvements

[Kishi85]

Description

• Adds error handling in case the portal does not return a stream that can be used (potential for out-of-bounds read on the vector for the fallback stream)
• Ensure pipewire modules are loaded only when needed during portal_display() and not early during portal_display_names() enumeration. Otherwise Pipewire might be initialized even when never used.
• Fix some code issues (as reported by SonarQube for IDE)

Screenshot

Issues Fixed or Closed

Roadmap Issues

Type of Change

• feat: New feature (non-breaking change which adds functionality)
• fix: Bug fix (non-breaking change which fixes an issue)
• docs: Documentation only changes
• style: Changes that do not affect the meaning of the code (white-space, formatting, missing semicolons, etc.)
• refactor: Code change that neither fixes a bug nor adds a feature
• perf: Code change that improves performance
• test: Adding missing tests or correcting existing tests
• build: Changes that affect the build system or external dependencies
• ci: Changes to CI configuration files and scripts
• chore: Other changes that don't modify src or test files
• revert: Reverts a previous commit
• BREAKING CHANGE: Introduces a breaking change (can be combined with any type above)

Checklist

• Code follows the style guidelines of this project
• Code has been self-reviewed
• Code has been commented, particularly in hard-to-understand areas
• Code docstring/documentation-blocks for new or existing methods/components have been added or updated
• Unit tests have been added or updated for any new or modified functionality

AI Usage

• None: No AI tools were used in creating this PR
• Light: AI provided minor assistance (formatting, simple suggestions)
• Moderate: AI helped with code generation or debugging specific parts
• Heavy: AI generated most or all of the code changes

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov]

Bundle Report

Bundle size has no change ✅

[codecov]

Codecov Report

❌ Patch coverage is 12.50000% with 7 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (master@94137da). Learn more about missing BASE report.
⚠️ Report is 1 commits behind head on master.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/platform/linux/portalgrab.cpp	12.50%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #4979   +/-   ##
=========================================
  Coverage          ?   17.96%           
=========================================
  Files             ?      108           
  Lines             ?    23424           
  Branches          ?    10340           
=========================================
  Hits              ?     4209           
  Misses            ?    15813           
  Partials          ?     3402           

Flag	Coverage Δ
Archlinux	11.60% <0.00%> (?)
FreeBSD-14.3-amd64	13.59% <12.50%> (?)
Homebrew-ubuntu-22.04	13.92% <0.00%> (?)
Linux-AppImage	12.21% <12.50%> (?)
Windows-AMD64	14.90% <ø> (?)
Windows-ARM64	13.22% <ø> (?)
macOS-arm64	19.02% <ø> (?)
macOS-x86_64	18.37% <ø> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/platform/linux/portalgrab.cpp	4.54% <12.50%> (ø)

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