repair panic (#1999)

* repair panic

* Add empty struct field test

Co-authored-by: Lea Anthony <lea.anthony@gmail.com>

v2/internal/binding/binding_test/binding_emptystruct_test.go

@@ -0,0 +1,53 @@
+package binding_test
+
+type EmptyStruct struct {
+	Empty struct{} `json:"empty"`
+}
+
+func (s EmptyStruct) Get() EmptyStruct {
+	return s
+}
+
+var EmptyStructTest = BindingTest{
+	name: "EmptyStruct",
+	structs: []interface{}{
+		&EmptyStruct{},
+	},
+	exemptions:  nil,
+	shouldError: false,
+	want: `
+export namespace binding_test {
+	export class EmptyStruct {
+		// Go type: struct {}
+
+		empty: any;
+
+		static createFrom(source: any = {}) {
+			return new EmptyStruct(source);
+		}
+		constructor(source: any = {}) {
+			if ('string' === typeof source) source = JSON.parse(source);
+			this.empty = this.convertValues(source["empty"], null);
+		}
+		convertValues(a: any, classs: any, asMap: boolean = false): any {
+			if (!a) {
+				return a;
+			}
+
+			if (a.slice) {
+				return (a as any[]).map(elem => this.convertValues(elem, classs));
+			} else if ("object" === typeof a) {
+				if (asMap) {
+					for (const key of Object.keys(a)) {
+						a[key] = new classs(a[key]);
+					}
+					return a;
+				}
+				return new classs(a);
+			}
+			return a;
+		}
+	}
+}
+`,
+}