loggingexporter: fix handling the loop for empty attributes

[pmm-sumo]

Description:

When span was containing several events, only the first one was printed out by the logging exporter. After checking the code it, turned out that handling the case with no attributes returns from the iteration loop altogether, which is wrong. The same bug was introduced for span links.

Link to tracking Issue: N/A

Testing: Just manual tests performed for Span Events

Documentation: N/A

[codecov]

Codecov Report

Merging #2610 (3ce79b5) into main (bf8b945) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #2610   +/-   ##
=======================================
  Coverage   92.02%   92.02%           
=======================================
  Files         271      271           
  Lines       15446    15446           
=======================================
  Hits        14214    14214           
  Misses        850      850           
  Partials      382      382           

Impacted Files	Coverage Δ
exporter/loggingexporter/logging_exporter.go	96.28% <100.00%> (ø)

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