Fix validation for empty SMB share name

We weren't raising a validation error on empty string for SMB
share name.

src/middlewared/middlewared/plugins/smb.py

@@ -1467,6 +1467,12 @@ async def validate_share_name(self, name, schema_name, verrors, exist_ok=True):
                 f'{name} is a reserved section name, please select another one'
             )
 
+        if len(name) == 0:
+            verrors.add(
+                f'{schema_name}.name',
+                'Share name may not be an empty string.'
+            )
+
         invalid_characters = INVALID_SHARE_NAME_CHARACTERS & set(name)
         if invalid_characters:
             verrors.add(
@@ -1518,7 +1524,7 @@ async def validate(self, data, schema_name, verrors, old=None):
                 'of SMB share.'
             )
 
-        if data.get('name'):
+        if data.get('name') is not None:
             await self.validate_share_name(data['name'], schema_name, verrors)
 
         if data.get('path_suffix') and len(data['path_suffix'].split('/')) > 2:
@@ -1583,7 +1589,7 @@ async def share_precheck(self, data):
                     'at least one local SMB user before creating an SMB share.'
                 )
 
-        if data.get('name'):
+        if data.get('name') is not None:
             await self.validate_share_name(data['name'], 'sharing.smb.share_precheck', verrors, False)
 
         verrors.check()