panic on current_predicate with a / in the module qualification.

[dougransom]

doug@kite:~/code/scryer-prolog/target/release$ env RUST_BACKTRACE=1 ./scryer-prolog  -f -v
v0.10.0-17-ge4d96925
doug@kite:~/code/scryer-prolog/target/release$ env RUST_BACKTRACE=1 ./scryer-prolog  -f 
?- current_predicate(http/http_open:X).

thread 'main' (479529) panicked at src/machine/system_calls.rs:3996:17:
internal error: entered unreachable code
stack backtrace:
   0: __rustc::rust_begin_unwind
             at /rustc/ed61e7d7e242494fb7057f2657300d9e77bb4fcb/library/std/src/panicking.rs:698:5
   1: core::panicking::panic_fmt
             at /rustc/ed61e7d7e242494fb7057f2657300d9e77bb4fcb/library/core/src/panicking.rs:75:14
   2: core::panicking::panic
             at /rustc/ed61e7d7e242494fb7057f2657300d9e77bb4fcb/library/core/src/panicking.rs:145:5
   3: scryer_prolog::machine::system_calls::<impl scryer_prolog::machine::Machine>::get_db_refs
             at /home/doug/code/scryer-prolog/src/machine/system_calls.rs:3996:17
   4: scryer_prolog::machine::dispatch::<impl scryer_prolog::machine::Machine>::dispatch_loop
   5: scryer_prolog::machine::Machine::run_module_predicate
             at /home/doug/code/scryer-prolog/src/machine/mod.rs:269:29
   6: scryer_prolog::run_binary::{{closure}}
             at /home/doug/code/scryer-prolog/src/lib.rs:81:13
   7: tokio::runtime::park::CachedParkThread::block_on::{{closure}}
             at /home/doug/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tokio-1.45.0/src/runtime/park.rs:284:71
   8: tokio::task::coop::with_budget
             at /home/doug/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tokio-1.45.0/src/task/coop/mod.rs:167:5
   9: tokio::task::coop::budget
             at /home/doug/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tokio-1.45.0/src/task/coop/mod.rs:133:5
  10: tokio::runtime::park::CachedParkThread::block_on
             at /home/doug/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tokio-1.45.0/src/runtime/park.rs:284:31
  11: tokio::runtime::context::blocking::BlockingRegionGuard::block_on
             at /home/doug/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tokio-1.45.0/src/runtime/context/blocking.rs:66:14
  12: tokio::runtime::scheduler::multi_thread::MultiThread::block_on::{{closure}}
             at /home/doug/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tokio-1.45.0/src/runtime/scheduler/multi_thread/mod.rs:87:22
  13: tokio::runtime::context::runtime::enter_runtime
             at /home/doug/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tokio-1.45.0/src/runtime/context/runtime.rs:65:16
  14: tokio::runtime::scheduler::multi_thread::MultiThread::block_on
             at /home/doug/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tokio-1.45.0/src/runtime/scheduler/multi_thread/mod.rs:86:9
  15: tokio::runtime::runtime::Runtime::block_on_inner
             at /home/doug/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tokio-1.45.0/src/runtime/runtime.rs:358:50
  16: tokio::runtime::runtime::Runtime::block_on
             at /home/doug/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tokio-1.45.0/src/runtime/runtime.rs:330:18
  17: scryer_prolog::run_binary
             at /home/doug/code/scryer-prolog/src/lib.rs:77:13
  18: core::ops::function::FnOnce::call_once
             at /rustc/ed61e7d7e242494fb7057f2657300d9e77bb4fcb/library/core/src/ops/function.rs:250:5
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
doug@kite:~/code/scryer-prolog/target/release$