optimise performance of tag_controller show

[Tlazypanda]

Fixes #8072

optimised performance of tag_controller show by replacing .length>0 with size.positive? so that sql queries are not repeated and response time is reduced.

• PR is descriptively titled 📑 and links the original issue above 🔗
• tests pass -- look for a green checkbox ✔️ a few minutes after opening your PR -- or run tests locally with rake test
• code is in uniquely-named feature branch and has no merge conflicts 📁
• screenshots/GIFs are attached 📎 in case of UI updation
• ask @publiclab/reviewers for help, in a comment below

Screenshots

Before

After

Thanks!

[codecov]

Codecov Report

Merging #8073 into master will increase coverage by 1.88%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #8073      +/-   ##
==========================================
+ Coverage   80.52%   82.41%   +1.88%     
==========================================
  Files          99       99              
  Lines        5757     5737      -20     
==========================================
+ Hits         4636     4728      +92     
+ Misses       1121     1009     -112     

Impacted Files	Coverage Δ
app/controllers/tag_controller.rb	81.40% <100.00%> (+5.48%)	⬆️
app/models/node.rb	91.07% <0.00%> (+0.36%)	⬆️
app/api/srch/search.rb	66.24% <0.00%> (+0.63%)	⬆️
app/controllers/users_controller.rb	82.29% <0.00%> (+1.04%)	⬆️
app/helpers/application_helper.rb	84.52% <0.00%> (+1.19%)	⬆️
app/controllers/admin_controller.rb	79.74% <0.00%> (+1.68%)	⬆️
app/controllers/search_controller.rb	97.67% <0.00%> (+2.32%)	⬆️
app/controllers/wiki_controller.rb	85.00% <0.00%> (+3.07%)	⬆️
app/models/concerns/node_shared.rb	90.29% <0.00%> (+3.39%)	⬆️
... and 8 more

[Tlazypanda]

Hey @jywarren @cesswairimu can you kindly review? Thanks ✌️

[jywarren]

Wow, how cool. Love the quantitative approach here!!!