Fix crash when nativeSymbol index is out of bounds in assembly view

[fatadel]

Closes #5819.

The root cause is at this line.
nativeSymbols[currentNativeSymbol] will yield undefined when nativeSymbols is empty (eg, frame does not have native symbols). And this is exactly the case because we set initialNativeSymbol: 0.

Fixed by returning null instead of undefined, which is handled fine in the downstream code.

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Use the same instructions as in the original issue on this profile to see the issue gone.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.56%. Comparing base (37b31b0) to head (e09282c).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5850   +/-   ##
=======================================
  Coverage   85.56%   85.56%           
=======================================
  Files         319      319           
  Lines       31420    31424    +4     
  Branches     8661     8665    +4     
=======================================
+ Hits        26885    26889    +4     
  Misses       4104     4104           
  Partials      431      431           

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[mstange]

Could we instead make it so that currentNativeSymbol is always either in-bounds or null? I.e. make it null in the case where the symbol list is empty.

[fatadel]

Done ✅ Good feedback, thank you @mstange!