Don’t allow use of $ param with no value in queries

Beforehand it was possible to do  SELECT * FROM $  which would show all of the variables defined. This is now not possible, and variables must be specified using their defined name.

db/fetch.go

@@ -106,6 +106,8 @@ func (e *executor) fetch(ctx context.Context, val interface{}, doc *data.Doc) (o
 
 	case *sql.Param:
 
+		if len(val.ID) > 0 {
+
 			for _, s := range paramSearchKeys {
 
 				if obj, ok := ctx.Value(s).(*data.Doc); ok {
@@ -134,6 +136,8 @@ func (e *executor) fetch(ctx context.Context, val interface{}, doc *data.Doc) (o
 
 			}
 
+		}
+
 		return nil, nil
 
 	case *sql.RunStatement: