Fix crash when target(in Value.preserveToString) is undefined

[gnh1201]

#467

[codecov-commenter]

Codecov Report

Merging #470 (d00ef8f) into master (8d44bc1) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #470   +/-   ##
=======================================
  Coverage   86.05%   86.05%           
=======================================
  Files           2        2           
  Lines        2352     2352           
  Branches      607      607           
=======================================
  Hits         2024     2024           
  Misses        328      328           

Impacted Files	Coverage Δ
es6-shim.js	87.57% <100.00%> (ø)

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[ljharb]

Just like with the previous change, I would much prefer to locate the specific caller of ES.preserveToString rather than papering over the problem here.

[gnh1201]

* typeof(globals.Reflect): object
* typeof(ReflectShims.defineProperty): undefined   <-- error
overrideNative(globals.Reflect, 'defineProperty', ReflectShims.defineProperty);

This means that globals.Reflect variable is going to be undefined.

How can I fix a problem that ReflectShims.defineProperty is undefined?

[ljharb]

Ah - if Reflect exists but Reflect.defineProperty does not, then that block of code should do branch, and call defineProperty versus overrideNative.

[gnh1201]

Found a better solution.

[ljharb]

@gnh1201 what better solution? Is #467 still an issue?