chore(internal): codegen related update

Author: stainless-app[bot]

src/core.ts

@@ -1054,10 +1054,10 @@ export const ensurePresent = <T>(value: T | null | undefined): T => {
  */
 export const readEnv = (env: string): string | undefined => {
   if (typeof process !== 'undefined') {
-    return process.env?.[env]?.trim() ?? undefined;
+    return process.env?.[env]?.trim() || undefined;
   }
   if (typeof Deno !== 'undefined') {
-    return Deno.env?.get?.(env)?.trim();
+    return Deno.env?.get?.(env)?.trim() || undefined;
   }
   return undefined;
 };