[DanielVdWP]

Description

Fixes #172.

Cube dimension labels currently display an underscore (_) when a
custom variable contains the numeric value 0 or the string "0".

This happens because the dimension label renderer uses PHP's shorthand
ternary operator (?:), which treats zero values as falsy.

Changes

• Preserve numeric and string zero values when rendering dimension labels.
• Continue displaying _ for null, empty string, and false values.
• Apply the fix to the shared dimension widget, covering both host
  and service cubes.

Testing

The following cases were verified locally using PHP 8.4:

• Integer zero: displays 0.
• String zero: displays 0.
• Floating-point zero: displays 0.
• Null: displays _.
• Empty string: displays _.
• Boolean false: displays _.
• Non-zero integers and ordinary strings: remain unchanged.

The regression was reproduced against the original implementation.

PHP syntax validation passed.

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