I'm fairly new to Mac so forgive me if this is common knowledge but Spell Catcher has a setting that prevents double spaces while typing. A simple "shift-space" overrides the setting. The program works in virtually all Mac software and has cured the problem for me with Pages crashing in the example you mentioned. Spell Catcher has a huge number of options; some choices are hard to find so...Preferences/Interactive/Automatic will take you to the section you need.
Other software must offer this option, I suppose, but this is the first one I found and I use it every day.