fix(eslint-plugin): [triple-slash-reference] fix crash with external module reference

[ddubrava]

fixes #2762

https://astexplorer.net/#/gist/cde0bd7d85e03d135e604e7913a999cd/c034332f4ccf256e809629b0552578191e38b3fe

I'm not sure about the solution cuz it's weird that there was used as TSESTree.TSExternalModuleReference and didn't handle any other types considering that moduleReference has already been typed.

[typescript-eslint]

Thanks for the PR, @ddubrava!

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The core maintainers work on this in their personal time, so please understand that it may not be possible for them to review your work immediately.

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[codecov]

Codecov Report

Merging #2788 (d6d15bf) into master (e82698c) will decrease coverage by 0.00%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master    #2788      +/-   ##
==========================================
- Coverage   92.79%   92.79%   -0.01%     
==========================================
  Files         297      300       +3     
  Lines        9833     9858      +25     
  Branches     2762     2770       +8     
==========================================
+ Hits         9125     9148      +23     
  Misses        332      332              
- Partials      376      378       +2     

Flag	Coverage Δ
unittest	92.79% <66.66%> (-0.01%)	⬇️

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

Impacted Files	Coverage Δ
.../eslint-plugin/src/rules/triple-slash-reference.ts	93.54% <66.66%> (-3.12%)	⬇️
packages/eslint-plugin/src/rules/array-type.ts	97.33% <0.00%> (-1.30%)	⬇️
packages/scope-manager/src/lib/index.ts	100.00% <0.00%> (ø)
packages/scope-manager/src/lib/es2020.ts	100.00% <0.00%> (ø)
packages/scope-manager/src/lib/esnext.ts	100.00% <0.00%> (ø)
packages/visitor-keys/src/visitor-keys.ts	100.00% <0.00%> (ø)
packages/eslint-plugin/src/rules/ban-types.ts	100.00% <0.00%> (ø)
...ackages/eslint-plugin/src/rules/no-implied-eval.ts	93.75% <0.00%> (ø)
...ckages/eslint-plugin/src/rules/no-throw-literal.ts	95.00% <0.00%> (ø)
...eslint-plugin/src/rules/no-unsafe-member-access.ts	100.00% <0.00%> (ø)
... and 7 more

[bradzacher]

I think we should just completely ignore these cases by returning early instead.

There's no import source to compare against here, so doing so will likely lead to some weirdness.

[bradzacher]

thanks for this!