fix: simplify null checks for reasoning and content (#135)

* fix: simplify null checks for reasoning and content in OpenRouterChatLanguageModel

* fix(test): ci

Author: DeJeune

src/chat/index.test.ts

@@ -660,11 +660,6 @@ describe('doStream', () => {
         type: 'response-metadata',
         modelId: 'gpt-3.5-turbo-0613',
       },
-      {
-        type: 'text-start',
-        id: expect.any(String),
-      },
-      { type: 'text-delta', delta: '', id: expect.any(String) },
       {
         type: 'response-metadata',
         id: 'chatcmpl-96aZqmeDpA9IPD6tACY8djkMsJCMP',
@@ -673,6 +668,7 @@ describe('doStream', () => {
         type: 'response-metadata',
         modelId: 'gpt-3.5-turbo-0613',
       },
+      { type: 'text-start', id: expect.any(String) },
       { type: 'text-delta', delta: 'Hello', id: expect.any(String) },
       {
         type: 'response-metadata',

src/chat/index.ts

@@ -560,11 +560,11 @@ export class OpenRouterChatLanguageModel implements LanguageModelV2 {
                   }
                 }
               }
-            } else if (delta.reasoning != null) {
+            } else if (delta.reasoning) {
               emitReasoningChunk(delta.reasoning);
             }
 
-            if (delta.content != null) {
+            if (delta.content) {
               if (!textStarted) {
                 textId = openrouterResponseId || generateId();
                 controller.enqueue({