minor fixes (#1194)

* minor fixes

* fix build errors

mlx/event.h

@@ -10,46 +10,46 @@ namespace mlx::core {
 
 class Event {
  public:
-  Event() {};
+  Event() = default;
 
   Event(const Stream& steam);
 
-  // Wait for the event to be signaled at its curent value
+  // Wait for the event to be signaled at its current value
   void wait();
 
   // Signal the event at its current value
   void signal();
 
   // Check if the event is valid
-  bool valid() {
+  bool valid() const {
     return event_ != nullptr;
-  };
+  }
 
-  uint64_t value() {
+  uint64_t value() const {
     return value_;
-  };
+  }
 
   void set_value(uint64_t v) {
     value_ = v;
-  };
+  }
 
-  const Stream& stream() {
+  const Stream& stream() const {
     if (!valid()) {
       throw std::runtime_error(
           "[Event::stream] Cannot access stream on invalid event.");
     }
     return stream_;
-  };
+  }
 
-  const std::shared_ptr<void>& raw_event() {
+  const std::shared_ptr<void>& raw_event() const {
     return event_;
-  };
+  }
 
  private:
   // Default constructed stream should never be used
   // since the event is not yet valid
   Stream stream_{0, Device::cpu};
-  std::shared_ptr<void> event_{nullptr};
+  std::shared_ptr<void> event_;
   uint64_t value_{0};
 };