restore exception validation logic with proper operator

app/src/api/services/domainLogic/validateUpdate.ts

@@ -24,8 +24,10 @@ function canEdit(key: string, allowDerived: boolean = false) {
 
 export function validateFieldChange(field: string, value: any, isExternal: boolean = true) {
     if(!isDefined(field)) {
+        if(field !== 'is_extension'){
             throw new InvalidFieldError('Field does not exist', field);
         }
+    }
     
     const allowDerived = !isExternal;
     if(!canEdit(field, allowDerived)) {