fix(microservices): fix redundant code to emit error

[youngkiu]

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• The commit message follows our guidelines: https://github.com/nestjs/nest/blob/master/CONTRIBUTING.md
• Tests for the changes have been added (for bug fixes / features)
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PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Other... Please describe:

What is the current behavior?

Issue Number: N/A

What is the new behavior?

Does this PR introduce a breaking change?

• Yes
• No

Other information

From #13195

              call.emit('error', err);
              subscription.unsubscribe();
              reject(err);

The bug was fixed by adding call.emit('error', err) before subscription.unsubscribe().

      try {
        await this.writeObservableToGrpc(result$, call);
      } catch (err) {
        call.emit('error', err);
        return;
      }

The call.emit('error', err); of the catch statement by reject() is a code that does not work because it follows subscription.unsubscribe();.

If you only look at the try catch statement without looking inside the writeObservableToGrpc() function, call.emit('error', err); is a misleading code and should be deleted.

[coveralls]

Pull Request Test Coverage Report for Build c47557dc-e8dd-414c-beb0-7598c1a72576

Details

• 2 of 2 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.02%) to 92.181%

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Totals
Change from base Build 14a5790e-1a63-471c-9a82-c6e1ef81c364:	0.02%
Covered Lines:	6732
Relevant Lines:	7303

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💛 - Coveralls

[kamilmysliwiec]

LGTM