Some people feel there should be an exception to this rule for single-character errors in code. (There is a general consensus that single-character errors in sentences are highly unlikely to matter.) My approach to this is:
If it's not your question, and you see a one-character typo, your ANSWER is "hey, OP, you have a one character typo: you have [line paste] where you should have [corrected line].
If it's your question, you update it and add "Update: Sorry, when sanitizing this code I made a one-character typo: the code that causes the problem did not have [error] where it should be [correction] and I've corrected my sanitized version in this question." Now the 400+ answerers who are telling you about the typo can delete their answers.
Either way, you avoid the single-character edit.