Description

clearing glyph for marker annotation in styler was causing an error

Issues

• Fix Annotation icon select form should not be clearable #3154

Please check if the PR fulfills these requirements

• The commit message follows our guidelines: https://github.com/geosolutions-it/MapStore2/blob/master/CONTRIBUTING.md
• 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", remove the others)

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

What is the current behavior? (You can also link to an open issue here)
there is an error thrown in the console.

What is the new behavior?
the error is no longer thrown in the console.

Does this PR introduce a breaking change? (check one with "x", remove the other)

• Yes
• No

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

Other information: