Panics (overflows) on parse fuzz target

I did more fuzz runs on the `parse` fuzz target and detected the following panics/issues: * `pdf/pdf/src/enc.rs:304:24` capacity overflow * `pdf/pdf/src/object/function.rs:152:100` attempt to subtract with overflow * UNKNOWN stack overflow I used code of the commit `f87d3f5e90bddc9df8e0e144b06f2727e7afcc7e`. I attached panic inducing inputs the fuzzer generated that caused the respective panics: [pdf_panic_inputs.zip](https://github.com/user-attachments/files/20187333/pdf_panic_inputs.zip)