fix: faulty type spec for untyped objects

Author: efcasado

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ElixirClientCodegen.java

@@ -875,6 +875,7 @@ private void buildTypespec(CodegenProperty property, StringBuilder sb) {
             if (property == null) {
                 LOGGER.error(
                         "CodegenProperty cannot be null. Please report the issue to https://github.com/openapitools/openapi-generator with the spec");
+                sb.append("any()");
             } else if (property.isArray) {
                 sb.append("list(");
                 buildTypespec(property.items, sb);