fix: ignore empty allowed or forbidden

[alestiago]

Description

Ignores empty allow or forbidden.

After

very_good packages check licenses --allowed="" --forbidden="" 
# Reports, equivalent to `very_good packages check licenses`

very_good packages check licenses --allowed="MIT" --forbidden="" 
# Reports with allowed, equivalent to `very_good packages check licenses --allowed="MIT"`

very_good packages check licenses --allowed="" --forbidden="MIT" 
# Reports with forbidden, equivalent to `very_good packages check licenses --forbidden="MIT"`

Before

very_good packages check licenses --allowed="" --forbidden="" 
# Throws usage exception, cannot specify both allowed and forbidden options.

very_good packages check licenses --allowed="MIT" --forbidden="" 
# Throws usage exception, cannot specify both allowed and forbidden options.

very_good packages check licenses --allowed="" --forbidden="MIT" 
# Throws usage exception, cannot specify both allowed and forbidden options.

Type of Change

• ✨ New feature (non-breaking change which adds functionality)
• 🛠️ Bug fix (non-breaking change which fixes an issue)
• ❌ Breaking change (fix or feature that would cause existing functionality to change)
• 🧹 Code refactor
• ✅ Build configuration change
• 📝 Documentation
• 🗑️ Chore

[erickzanardo]

Two optional nits, but looks great!