bean property path extension: have get return a non-nullable string

Author: emmanueltouzery

typescript-generator-core/src/main/java/cz/habarta/typescript/generator/ext/BeanPropertyPathExtension.java

@@ -52,14 +52,14 @@ private static void emitFieldsClass(Writer writer, Settings settings) {
         List<String> fieldsClassLines = Arrays.asList(
             "class Fields {",
             "    protected $$parent: Fields | undefined;",
-            "    protected $$name: string | undefined;",
+            "    protected $$name: string;",
             "    constructor(parent?: Fields, name?: string) {",
             "        this.$$parent = parent;",
-            "        this.$$name = name;",
+            "        this.$$name = name || '';",
             "    };",
-            "    get(): string | undefined {",
-            "        if (this.$$parent && this.$$parent.get()) {",
-            "            return this.$$name ? this.$$parent.get() + \".\" + this.$$name : this.$$parent.get();",
+            "    get(): string {",
+            "        if (this.$$parent && this.$$parent.get().length > 0) {",
+            "            return this.$$parent.get() + \".\" + this.$$name;",
             "        } else {",
             "            return this.$$name;",
             "        }",