Merge pull request #380 from batanus/make-index-optional

Author: nezhyborets

Sources/OpenAI/Public/Models/ChatStreamResult.swift

@@ -71,7 +71,7 @@ public struct ChatStreamResult: Codable, Equatable, Sendable {
 
             public struct ChoiceDeltaToolCall: Codable, Equatable, Sendable {
 
-                public let index: Int
+                public let index: Int?
                 /// The ID of the tool call.
                 public let id: String?
                 /// The function that the model called.