Fix multi-dropdown field can't have no options selected (#8391)

Fixes: #8224 

1. Summary
All multi-dropdowns across the application don't accept empty options
because emptiness is perceived as an invalid state.

2. Solution
The issue came down to the back-end and the specific string utility
function that converts a string separated by `,` to an array of options.
But the problem with it is that it returns `['']` for an empty string
representing an emptiness. And then `['']` fails on the parser because
simply `''` is not a valid option the user selected for the dropdown. So
I updated the string utility function to return an empty array for cases
like `'', '{}', '{ }'`, etc

3. Recording


https://github.com/user-attachments/assets/071fe5d2-2123-4deb-878c-67f62d9b3431

packages/twenty-server/src/engine/twenty-orm/utils/format-result.util.ts

@@ -148,7 +148,9 @@ function formatFieldMetadataValue(
     (fieldMetadata.type === FieldMetadataType.MULTI_SELECT ||
       fieldMetadata.type === FieldMetadataType.ARRAY)
   ) {
-    return value.replace(/{|}/g, '').split(',');
+    const cleanedValue = value.replace(/{|}/g, '').trim();
+
+    return cleanedValue ? cleanedValue.split(',') : [];
   }
 
   return value;