So, he can fly-- which can be logically deduced to be more difficult to do than using Energy blasts by the series itself. I already said Gohan had to teach Videl how to project ki spheres before she could learn to fly. Goku, Roshi, Krillin, many characters couldn't fly but could throw blasts with ease, even Fodder Frieza Soldiers could do it. If Guldo is skilled enough to learn how to fly, I don't think it's a stretch to say he can throw an energy blast. This is like saying the Tsuchikage can't walk on water, something every ninja above Genin level has been able to do.
Flying is harder to do than firing energy blasts, as many characters were unable to fly in early DB despite the fact that they can easily fire energy blasts, on top of the fact that Videl's training heavily implies learning to project Ki is necessary to learning how to fly. Videl made a fricken energy sphere, and (whether or not this is still Canon or not is unknown) Gohan published books that taught everyone to use energy blasts and Ki and shit. Even if Dragonball Online isn't Canon anymore, Videl is a relatively normal human, nowhere near as talented as even Yamcha, and he knew how to fire energy. Primal Aliens with no intelligence at all can use Ki and fly too, nevermind the fact that it seems like most aliens just have natural talent with this Ki stuff. Pan knew how to fly and release her aura before she could even talk. Gohan learned how to fire Ki blasts by himself-- that's how he cooked lizard tails to eat. The only character who I would doubt have the ability to fly but not use Energy blasts would be Dende from Name saga. But even then, I have a hard time accepting the idea that Dende can't create a ball of Chi-- but he can fly and heal people. Dende might not have any potency with his Ki blasts, but I am certain he can at least do what Videl did. The only other idea that supports Dende not being able to fire lasers is that he's a child that has no inclination for combat. Whereas Guldo is an Elite Ginyu Force member who should have some skill with Ki Manipulation comparable to initial Kid Goku at the least.
If Guldo can fly with a decent amount of skill, and he's supposed to be an Elite Warrior (even if he's just there because of his hax), he must likely be able to throw an energy blast. If you're argument is that none of the characters I mentioned above are Guldo, and just because they can fire energy blasts doesn't mean Guldo can, I would only agree with that statement if the idea that flight, being an alien in Dragon Ball, and being a fighter of any worth in Dragon Ball doesn't imply some minor form of Ki Energy projection.
I will repeat what I said before, it makes less sense for Guldo to be unable to manipulate Ki in a way even comparable to Initial Kid Goku and Gohan, given the context surrounding his placement in the verse and skill set, as well as how those skills seem to correlate with each other.
Your reasoning seems to be the fact that we have no concrete evidence that he can fire an energy blast or even create an energy sphere, that he can't do it. Meaning your conclusion is based on a lack of evidence, rather than any ideas surrounding your conclusion to support it. Making it argument from ignorance.
This is a greater leap in logic than to assume he can do it.
TL DR: Kukui, why do you refuse to make logical assumptions and remain in disbelief whenever there is no hard evidence to prove you wrong-- despite the fact that the context around the verse can give you an answer that is likely possible? If Guldo's profile in your head doesn't have offensive and utility Ki Manipulation, it should at the very least be listed as "Likely," just as everyone stronger than Gotenks should have limited Space-time Manipulation.
