Bugfix: Avoid potential crash from force-unwrap of pointOrigin in pan gesture

[rm335]

💡 Description

Fixes a potential crash in the Tracking Protection menus where pointOrigin! was force-unwrapped inside panGestureRecognizerAction(sender:). The property is optional and only initialized in viewDidLayoutSubviews, so if the pan gesture fires before the first layout pass (e.g. after a memory warning, a rapid present/dismiss cycle, or in automated UI tests) the app crashes with EXC_BAD_INSTRUCTION.

The same bug pattern existed in two files (duplicated code path):

• firefox-ios/Client/Frontend/Browser/EnhancedTrackingProtection/EnhancedTrackingProtectionVC.swift — line 495
• firefox-ios/Client/Frontend/TrackingProtection/TrackingProtectionViewController.swift — line 707

The fix

The force-unwrap is replaced with the same safe-fallback pattern the surrounding code already uses just a few lines later (L504 / L716), defaulting to the current view origin (originalYPosition) when pointOrigin has not yet been set:

// Before
view.frame.origin = CGPoint(x: originalXPosition,
                            y: self.pointOrigin!.y + translation.y)

// After
view.frame.origin = CGPoint(x: originalXPosition,
                            y: (self.pointOrigin?.y ?? originalYPosition) + translation.y)

Behavior is identical in the common case where pointOrigin has been initialized (which is the only case the previous code handled correctly). Only the previously-crashing edge case is corrected.

Regression tests

Two new test files exercise the gesture handler with pointOrigin still nil (i.e. before viewDidLayoutSubviews ran) and verify the call no longer crashes:

• firefox-ios/firefox-ios-tests/Tests/ClientTests/TrackingProtectionTests/EnhancedTrackingProtectionVCTests.swift
• firefox-ios/firefox-ios-tests/Tests/ClientTests/TrackingProtectionTests/TrackingProtectionViewControllerTests.swift

Both test files follow the existing TrackingProtectionTests test-suite pattern (XCTest, @MainActor, @testable import Client, DependencyHelperMock().bootstrapDependencies()) and use a MockPanGestureRecognizer test double to drive the handler deterministically.

🎥 Demos

N/A — no visual change. Behavior is identical when pointOrigin is set (the common case). Only the previously-crashing edge case is corrected.

Static-grep verification

$ grep -rn "pointOrigin!" firefox-ios/Client --include="*.swift"
# (no output -- 0 hits)

📝 Checklist

• I filled in the ticket numbers and a description of my work
• I updated the PR name to follow our PR naming guidelines
• I ensured unit tests pass and wrote tests for new code
• If working on UI, I checked and implemented accessibility (Dynamic Text and VoiceOver) — N/A (no visible UI change)
• If adding telemetry, I read the data stewardship requirements and will request a data review — N/A
• If adding or modifying strings, I read the guidelines and will request a string review from l10n — N/A
• If needed, I updated documentation and added comments to complex code — no new code comments needed; fix uses the existing pattern from elsewhere in the same file.