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x11: Make damage region fetching code more robust to errors

With DamageReportNonEmpty damage report level, the x server will send kwin a DamageNotify when the damage region changes from empty to not empty.

The damage region will be made empty when SurfaceItemX11 calls xcb_damage_subtract().

It appears like xcb_generate_id() can return us an already associated XID, which eventually results in xcb_damage_subtract() failing and breaking state tracking in SurfaceItemX11. KWin will no longer receive DamageNotify events and some windows will freeze.

In order to make getting BadIdChoice less catastrophic, this change makes the SurfaceItemX11 reset m_isDamaged after successfully fetching the damage region. If xcb_generate_id() returns us a bad id, kwin will try to fetch the damage again in the next frame.

BUG: 456511

see also https://gitlab.freedesktop.org/xorg/lib/libxcb/-/issues/51#note_1579207

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