Why it's not crashing?

Several months ago, my colleagues encountered a very strange behavior of one of our processes after an exception was thrown. They told me that they know exactly that the process throws an exception which is not expected to be handled by their code, that is an exception must be unhandled and the process must be terminated immediately. But nothing like that happens. The process just continues its execution. At first, I thought that there must be some code down the stack which registers an exception handler that handles any exception indiscriminately. Therefore, the first thing I did was search for the try{}catch(…){} pattern down the stack. When I found nothing, I looked at the exception handlers list at the point where an exception was thrown.

It looked as follows:

0012fd14: USER32!_except_handler3+0 (7e440457)   CRT scope  0, func:   USER32!UserCallWinProc+10a (7e44aa1c) 0012fd6c: USER32!_except_handler3+0 (7e440457)   CRT scope  0, filter: USER32!DispatchMessageWorker+113 (7e440712)                 func:   USER32!DispatchMessageWorker+126 (7e44072a) 0012ffb0: VanishExcept!ILT+375(__except_handler3)+0 (0041117c) 0012ffe0: kernel32!_except_handler3+0 (7c839af0)   CRT scope  0, filter: kernel32!BaseProcessStart+29 (7c84377a)                 func:   kernel32!BaseProcessStart+3a (7c843790) Invalid exception stack at ffffffff

There were no user exception handlers at all, but instead was an exception handler I have not seen before:

0012fd14: USER32!_except_handler3+0 (7e440457)   CRT scope  0, func:   USER32!UserCallWinProc+10a (7e44aa1c) 0012fd6c: USER32!_except_handler3+0 (7e440457)   CRT scope  0, filter: USER32!DispatchMessageWorker+113 (7e440712)                 func:   USER32!DispatchMessageWorker+126 (7e44072a) 0012ffb0: VanishExcept!ILT+375(__except_handler3)+0 (0041117c) 0012ffe0: kernel32!_except_handler3+0 (7c839af0)   CRT scope  0, filter: kernel32!BaseProcessStart+29 (7c84377a)                 func:   kernel32!BaseProcessStart+3a (7c843790) Invalid exception stack at ffffffff