[AAE-3200] Attach button of content node selector becomes enabled when selecting a folder

[sivakumar414ram]

Please check if the PR fulfills these requirements

• The commit message follows our guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

What kind of change does this PR introduce? (check one with "x")

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

What is the current behaviour? (You can also link to an open issue here)

https://issues.alfresco.com/jira/browse/AAE-3200

What is the new behaviour?

Does this PR introduce a breaking change? (check one with "x")

• Yes
• No

If this PR contains a breaking change, please describe the impact and migration path for existing applications: ...

Other information:

[codecov-commenter]

Codecov Report

Merging #5946 into develop will increase coverage by 2.10%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           develop    #5946      +/-   ##
===========================================
+ Coverage    76.08%   78.18%   +2.10%     
===========================================
  Files          843      334     -509     
  Lines        18764     8939    -9825     
  Branches      3690     1779    -1911     
===========================================
- Hits         14276     6989    -7287     
+ Misses        3374     1399    -1975     
+ Partials      1114      551     -563     

Impacted Files	Coverage Δ
...t-node-selector/content-node-selector.component.ts	70.00% <100.00%> (+1.57%)	⬆️
...ib/document-list/services/document-list.service.ts	74.50% <0.00%> (-1.97%)	⬇️
.../lib/diagram/models/chart/multi-bar-chart.model.ts
lib/core/context-menu/context-menu.directive.ts
...ib/core/search-text/search-text-input.component.ts
...ponents/icons/diagram-icon-camel-task.component.ts
...m/components/widgets/typeahead/typeahead.widget.ts
...rocess/components/analytics-generator.component.ts
lib/core/services/bpm-user.service.ts
lib/core/pipes/multi-value.pipe.ts
... and 501 more

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