"Entity 12101 has no item?!" error message

In Creative Mode, flying around to explore a 200 x 200 block area, I had to exit fly mode and attempt to land on the ground in order to force Minecraft to draw the screen - as I have always had to do since the MC v1.5-era on multiple machines.

This time, I continued to fall without landing on the ground. I fell all the way to y=0, and only after taking a screenshot in this position did I return to the same position at a higher y value (forgot to take a screenshot at that time).

Checked the console log, and there was only one thing unusual (aside from the frequent "Can't keep up!" messages).

>>>
[15:08:14] [Client thread/INFO]: [CHAT] Saved screenshot as 2014-08-31_15.08.13.png
[15:08:18] [Client thread/ERROR]: Item entity 12101 has no item?!
[15:08:18] [Client thread/ERROR]: Item entity 12101 has no item?!
[15:08:18] [Client thread/ERROR]: Item entity 12101 has no item?!
>>>

The screenshot I attached is the one that was saved at 15:08:14 as shown above.