ArrayIndexOutOfBoundsException in `UTF8Reader` (ossfuzz)

[cowtowncoder]

(note: from Ossfuzz issue 32906: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=32906)

Looks like there is a boundary condition with UTF-8 codec.

[cowtowncoder]

Created FasterXML/woodstox#124 for this, issue reproducible on Woodstox (but once again, requires specific input source to get right boundary condition).

[cowtowncoder]

Fixed on Woodstox side, need to wait for 6.2.5 for a bit (anticipating some more reports still :) ).

(note that so far neither bug likely to occur for users, bit esoteric boundary conditions on invalid documents)