fix(sumologicexporter): don't send null logs

[pmalek-sumo]

To prevent sending null logs check if the body is not empty before attaching it like in the attached screenshot:

[kasia-kujawa]

Can the test case with sending null logs be added to unit tests? If yes, I recommend to add this.

[pmalek-sumo]

Can the test case with sending null logs be added to unit tests? If yes, I recommend to add this.

I wanted to do this but it seems that it's non trivial to make the exporter send the empty logs due to logic in appendAndSend, i.e. the provided body there is empty (which is ok) and we cannot really configure MaxRequestBodySize to force the flush (in order to check the asserts in tests).

I'm open to ideas to actually add a test for that.

ref:

sumologic-otel-collector/pkg/exporter/sumologicexporter/sender.go

Lines 400 to 438 in 2a5baaa

	func (s *sender) appendAndSend(
	ctx context.Context,
	line string,
	pipeline PipelineType,
	body *strings.Builder,
	flds fields,
	) (appendResponse, error) {
	var errors []error
	ar := newAppendResponse()
	if body.Len() > 0 && body.Len()+len(line) >= s.config.MaxRequestBodySize {
	ar.sent = true
	if err := s.send(ctx, pipeline, strings.NewReader(body.String()), flds); err != nil {
	errors = append(errors, err)
	}
	body.Reset()
	}
	if body.Len() > 0 {
	// Do not add newline if the body is empty
	if _, err := body.WriteString("\n"); err != nil {
	errors = append(errors, err)
	ar.appended = false
	}
	}
	if ar.appended {
	// Do not append new line if separator was not appended
	if _, err := body.WriteString(line); err != nil {
	errors = append(errors, err)
	ar.appended = false
	}
	}
	if len(errors) > 0 {
	return ar, consumererror.Combine(errors)
	}
	return ar, nil
	}