Light does travel in a straight line, or else there wouldn't be shades!! lol
The EM Wave
The EM wave is used to describe the possibilities of finding a particle at a certain location. But we can't say that the particle is at some particular point in the wave because then we lose the wave analogy. We can only say that the particle exists somewhere in the wave, and by that, we mean the particle is simultaneously everywhere on the wave.
So if the wave continues throughout the universe, that means at the next point in time, the particle could appear from anywhere throughout the universe.
So does that mean an electron near you could end up being at the edge of the universe at the very next moment? YES!!
But basically, the consequences of particles ending up at a very far distance is extremely low that it's considered never to happen.
In the Uncertainty Principle, there is this thing called action.
The action calculates the crest and troughs in a wave using the mass, time, and distance between the starting and final position of a particle or an object.
If say the final position of a particle is 10 units away(large distance for the particle say), the action of this would correspond to the crest of the wave(skipping the math); simultaneously, the same particle would also appear somewhere on that original wave, say, its 10.1 units away from the final position, the action would correspond to the trough of the wave. Lastly, we only have to add these waves together in order to get the final wave function for the final position of the wave.
The crest and the troughs cancel each other out, and so we get a final wave function of nearly zero possibility of finding the particle at such a large distance.
On the other hand, the possibilities of a particle ending up at a close location are huge. Because instead of canceling each other out, the waves stacks themselves up into a larger wave with much more amplitude, which means a higher chance of finding the particle at that location.
That's why the particles can't get far from their original position, and therefore you shouldn't be worried about its speed exceeding the speed of light.