Is having an extending blade near the knife handle a serious risk when cutting food?
No, there is not a risk to getting the kind of cut you describe, as long as you treat your knife with the respect it deserves. 

If there's a dull, raised part at the back of the knife, it is called the bolster, otherwise it's the heel of the blade.  The raised version is a common trait in forged knifes, and is supposed to add strength to the blade. 

 

From experience: yes, you can cut yourself on the heel of bolster-less knifes, but generally not in the way you describe. I would not avoid them, or avoid knives where the blade tapers from the handle for safety reasons. I've cut myself a couple times on the heel of the blade when grabbing for a knife in a hurry, but these kinds of cuts are generally superficial and fast healing. 

There is also a significant advantage to bolster-less blades: they're much easier to sharpen, and have more usable length to the blade.