Cleanup: Initialize instance variable before use to avoid Ruby warnings

[olleolleolle]

Description

This avoids a Ruby warning emitted on use.

By initializing the variable before use, this is an easy win against the sea of warnings output.

Testing

1. Run the test with RUBYOPT=-W2
2. See that @decorated_collection is not among the output

[n-rodriguez]

Hi there! Any news?

[n-rodriguez]

Ping @codebycliff

[n-rodriguez]

@olleolleolle can you please rebase your branch on master?

[olleolleolle]

I could make an attempt, in about 12 hours.

But I can hit the Update Branch button right now. If green, you could Squash commits Into One Commit, using the merge button variant for that.

[olleolleolle]

Haha, the issue is created by: me defining a variable, so the test must be altered to match that new situation!

Update: I updated the test, changing it to match the current code.

[n-rodriguez]

@olleolleolle thank you! Ping @codebycliff

[n-rodriguez]

ping @codebycliff