enhanced_security_compliance block: return nil if not defined in Terr…

…aform config

To fix 400 error on workspace creation

internal/services/databricks/databricks_workspace_resource.go

@@ -1220,7 +1220,7 @@ func expandWorkspaceEnhancedSecurity(input []interface{}) *workspaces.EnhancedSe
 	var config map[string]interface{}
 
 	if len(input) == 0 || input[0] == nil {
-		config = make(map[string]interface{})
+		return nil
 	} else {
 		config = input[0].(map[string]interface{})
 	}