tag_key doesn't work when sending json array to http input

[imankurpatel000]

Bug Report

Describe the bug
tag_key doesn't work when sending json array to http input.

To Reproduce

• Run fluent-bit with the following configuration.

  [INPUT]
      name http
      listen 0.0.0.0
      port 8888
      tag_key key1
  
  [OUTPUT]
      name stdout
      match *
  

  fluent-bit -c fluent-bit.conf 

• send a json array to http://localhost:8888

  curl -d '[{"key1":"value1","key2":"value2"}]' -XPOST -H "content-type: application/json" http://localhost:8888

• View the output

  [0] http.0: [[1731488968.157629000, {}], {"key1"=>"value1", "key2"=>"value2"}]
  

  As you can see it didn't tag the record as value1 and instead it falls back to the default tag of http.0

• Now, send a json object to http://localhost:8888

  curl -d '{"key1":"value1","key2":"value2"}' -XPOST -H "content-type: application/json" http://localhost:8888

  and now the output is

  [0] value1: [[1731488986.817626000, {}], {"key1"=>"value1", "key2"=>"value2"}]
  

Expected behavior
It should tag the record properly as per the provided tag_key regardless if the data is sent as json object or array of json objects.

Your Environment

• Version used: 3.1.0

Additional context
The issue was introduced by #8794 which I believe was merged in 3.0.7 and 3.1.0. The issue is simple mistake of not setting the value of tag_from_record variable in the else block here.