Upload & Sell: On
I think its quite common for some bubbles to appear in some of these older glass. I think some of the other experts on this forum can elaborate, but my understanding is that sometimes some of these bubbles actually create a layer of coating on the lens to actually improve flare suppression. For example, quite a few of the prewar Zeiss Contax RF lenses have bubbles and its not an issue to use of one these lenses except for the collectors.
Most of the earlier Leitz lenses up to the 1950s have softer glass elements, I would be more concerned about cleaning marks, scratches or haze. That said, if you are concerned, there are plenty of Summitars out in the market, if you are patient, you can find a good one. Otherwise see if the seller is willing to refund the lens if you find that the bubble create IQ issues?
There are quite a lot of these vintage lenses out in the market with minty barrel and externals but with imperfect glass. Otherwise I know quite a few collectors buy two or even more lenses and swap parts/ elements to create a nice "collector".