PuTTY bug short-osc-crash

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summary: Crash with certain short forms of OSC escape sequences
class: bug: This is clearly an actual problem we want fixed.
absent-in: 0.76
present-in: cc10b68d313ec9e10e3186c4c953d2699f7de079 0.77 de66b0313a23d04312235cbf2054b882f554d21f
fixed-in: a7106d8eb26981a372ce7462d70d81a870a2a592 (0.78)

Certain terminal escape sequences sent by a server could lead to PuTTY using uninitialised data, and hence crashing or otherwise misbehaving.

A recent fix to escape sequence handling (a cut-down version of which went into 0.77) was intended to improve the handling of certain forms of OSC escape sequences that PuTTY doesn't recognise, such as ESC ] 112 BEL (interpreted by some terminals as 'reset cursor colour', and hence sent by some real servers). PuTTY has historically expected such sequences to contain a semicolon delimiter after the numeric part, and without that, PuTTY was interpreting the BEL character to cause an annoying literal beep.

Unfortunately, after that fix, the same form of escape sequence, while no longer causing beeps, can trigger the crash. This is now fixed.

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(last revision of this bug record was at 2022-10-28 21:01:18 +0100)