I strongly disagree, a Senior who cannot ask a "dumb question" is a useless developer to me. Ask away, we want to figure things out, we're not mind readers. Every good senior developer I know asks questions and admits when they don't know things. This is humility and in my eyes is a strong market for a good Senior Developer. The entire point of our job is to ask questions (to ourselves typically the most) and figure out the answers (the code).

Juniors could or should ask more questions, and by the time you're a Senior, you're asking key questions no matter how dumb they sound.