fix: app crash when opacity slider is moved to 0

[Kwonkunkun]

Changes

Motivation:

• When the opacity slider is moved to 0, the app crashes
• When the opacity slider is moved to 0, slider not visible

Modifications:

• add !! prefix check value
• erase opacity value in logic conditional render (detail in the commit)

Screenshots (optional)

• origin

• add !! prefix in logic conditional render

[vsalguero]

Thank you!