🥅 Better error handling for chatCompletion (huggingface#1080)

Thanks @chelsey-datasaur for the report.

Fix huggingface#1079 

cc @SBrandeis @hanouticelina for viz, as it handles messages from
`chatCompletion`

Author: coyotte508

packages/inference/src/tasks/custom/streamingRequest.ts

@@ -79,7 +79,16 @@ export async function* streamingRequest<T>(
 					}
 					const data = JSON.parse(event.data);
 					if (typeof data === "object" && data !== null && "error" in data) {
-						throw new Error(data.error);
+						const errorStr =
+							typeof data.error === "string"
+								? data.error
+								: typeof data.error === "object" &&
+								    data.error &&
+								    "message" in data.error &&
+								    typeof data.error.message === "string"
+								  ? data.error.message
+								  : JSON.stringify(data.error);
+						throw new Error(`Error forwarded from backend: ` + errorStr);
 					}
 					yield data as T;
 				}