chore: ensure empty message isnt sent

packages/opencode/src/session/message-v2.ts

@@ -476,7 +476,6 @@ export namespace MessageV2 {
           role: "assistant",
           parts: [],
         }
-        result.push(assistantMessage)
         for (const part of msg.parts) {
           if (part.type === "text")
             assistantMessage.parts.push({
@@ -535,6 +534,9 @@ export namespace MessageV2 {
             })
           }
         }
+        if (assistantMessage.parts.length > 0) {
+          result.push(assistantMessage)
+        }
       }
     }