Detected multiple panics (multiply with overflow) during fuzzing

[0x64617061]

I did fuzz runs using the fuzz_decode fuzz target with Rust overflow checks enabled and detected three different panics/issues:

1. jpeg-decoder/src/decoder.rs:1025:28 attempt to multiply with overflow
2. jpeg-decoder/src/decoder.rs:911:16 attempt to multiply with overflow
3. jpeg-decoder/src/decoder.rs:916:20 attempt to multiply with overflow

I have attached an archive with stack traces and the respective input files generated by the fuzzer.

jpeg-decoder_panics.zip

[fintelia]

This crate is in maintenance mode, so there's no one to triage fuzzing issues. If the fixes are straightforward enough, you're welcome to submit PRs to fix them, but we aren't looking to merge any big changes at this point