appmaker不匹配错误，我该如何解决？

Question

I have an error and i cant seem to resolve it:

Type mismatch: element at [0] should be string, but was: undefined Error: 
Type mismatch: element at [0] should be string, but was: undefined at 
datasources.SitesByld.script:1

Executing query for datasource SitesByld: (Error) : Type mismatch: element 
at [0] should be string, but was: undefined
at datasources.SitesByld.script:1
at Object.success (AppStart:11:14)

Executing query for datasource SitesByld failed.


var record = 
app.models.Sites.getRecord(query.parameters.SitesId);
if (record !== null) {
return [record];
}
return [];

I am fairly new to coding so forgive me if this is simple

Answer 1

At the end of your code, you have a if clause but there is no else clause? It seems like the function will always return an empty array.