xcode show error about first responder
macOS 10.12.5 
Xcode 8.3.3

according to the tutorial  [learnopengl](https://learnopengl.com/#!Getting-started/Hello-Window).  create window success, but xcode give me an error:
> ERROR: Setting <GLFWContentView: 0x100327d70> as the first responder for window <GLFWWindow: 0x104a028e0>, but it is in a different window ((null))! This would eventually crash when the view is freed. The first responder will be set to nil.
(
	0   AppKit                              0x00007fffc748f9cf -[NSWindow _validateFirstResponder:] + 557
	1   AppKit                              0x00007fffc6c0a74c -[NSWindow _setFirstResponder:] + 31
	2   AppKit                              0x00007fffc6cb29ce -[NSWindow _realMakeFirstResponder:] + 406
	3   AppKit                              0x00007fffc6cb27e4 -[NSWindow makeFirstResponder:] + 123
	4   openGl-1                            0x000000010000d68a _glfwPlatformCreateWindow + 678
	5   openGl-1                            0x000000010000924d glfwCreateWindow + 432
	6   openGl-1                            0x00000001000051b8 _ZN14OpenGLSession214createTriangleEv + 136
	7   openGl-1                            0x0000000100001504 main + 20
	8   libdyld.dylib                       0x00007fffde877235 start + 1
	9   ???                                 0x0000000000000001 0x0 + 1
)
I find the flew has same question and has fixed it, so I guessing and submit this issue.
maybe is just my code has problem.