Use null stream in ReactorNettyClientResponse if no body is available

Closes gh-32805

Author: poutsma

spring-web/src/main/java/org/springframework/http/client/ReactorNettyClientResponse.java

@@ -88,7 +88,7 @@ public InputStream getBody() throws IOException {
 		}
 
 		if (body == null) {
-			throw new IOException("Could not receive body");
+			body = InputStream.nullInputStream();
 		}
 		this.body = body;
 		return body;