Fixed cleanup on some Mir errors.

Release was called on invalid handles.

src/mir_init.c

@@ -46,7 +46,6 @@ int _glfwPlatformInit(void)
                         "Mir: Unable to connect to server: %s",
                         mir_connection_get_error_message(_glfw.mir.connection));
 
-        mir_connection_release(_glfw.mir.connection);
         return GL_FALSE;
     }
 

src/mir_window.c

@@ -410,7 +410,6 @@ static int createSurface(_GLFWwindow* window)
                         "Mir: Unable to create surface: %s",
                         mir_surface_get_error_message(window->mir.surface));
 
-        mir_surface_release_sync(window->mir.surface);
         return GL_FALSE;
     }