This is why you always use braces, even when they're optional. Imo a single-line if without braces is an accident waiting to happen.
Mind you, much of the C code I've co-maintained for the past while is compiler source, and compiler developers may be more attuned to seeing structured text as a parse tree.
Good for you!
But fortunately you put the braces in anyway, because the person who touches the code after you might be more prone to the mistake.
I almost never misspell things. I might therefore be tempted to believe that spell checkers are a pointless and annoying waste of time. But not everyone has the same brain as I, and experience has taught me that there are lots of people who can't spell well, many of whom are actually really good writers. I'd assume that the optional-braces problem is a cliche for a similar reason.
Another one is if(0 == some_thing). It seems clever and I try to use it, but if you write if(some_thing = 0), the compiler just warns you. So there's no real point in doing this.
The problem with compiler warnings is, unless you have a warning-free base build, they're difficult to see. And in turn, a warning-free build more or less depends on the very first developers to have turned the warning flags on while they were checking in stuff like mad trying to get someting to ship.
So, yeah, I could claim that I don't too many such silly mistakes (and that might even be true), but I can both understand and approve of such coding standards.
if (not_true) return;