Not unreasonable to be nervous but what you're doing might make matters worse.
Just ignore and keep walking at a steady pace, hands in pockets/by your side. If a dog does actually jump up, stand still, 'be a tree' and ask the owner to recall their dog (in as even a tone as you can manage).
Shouting, staring, waving hands, running, high pitched noises, kicking out - all more likely to wind a dog up, or if the dog is conflicted/anxious etc, trigger an aggressive response.
To be clear here - it isn't your problem what the dogs motivation is, the owner is at fault but - a bite or being tripped up and falling and getting hurt still hurts, even if it's someone else in the wrong.
If someone is sufficiently thoughtless and irresponsible as to let their dog go right up to you, there is no point shouting at them, they don't care and it won't alter how they behave in future. All you'll achieve is a higher likelyhood of injury to you, to the animal and a prolonged altercation.