fix(headers): use empty string for title

[satish-ravi]

Description

Fixes an iOS 18 only issue where header is shown as " "

Test plan

Tested on multiple versions across iOS and Android w/ @MuckT

Before	After

Related issues

• N/A

Backwards compatibility

yes

Network scalability

N/A

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.74%. Comparing base (312d7e0) to head (5c2e849).
Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6113   +/-   ##
=======================================
  Coverage   88.74%   88.74%           
=======================================
  Files         727      727           
  Lines       30785    30785           
  Branches     5623     5623           
=======================================
  Hits        27321    27321           
  Misses       3265     3265           
  Partials      199      199           

Files with missing lines	Coverage Δ
src/navigator/Headers.tsx	61.17% <ø> (ø)

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