Multi-window crashes in debug mode

[euclio]

OS: MacOS 10.12

Perhaps related to #401, but a different error. Running the multi_window example in debug mode crashes after the windows are displayed briefly. Release mode works as expected.

$ RUST_BACKTRACE=1 cargo run --bin multi_window
    Finished dev [unoptimized + debuginfo] target(s) in 0.0 secs
     Running `target/debug/multi_window`
thread 'main' panicked at 'Error InvalidOperation executing command: BindProgram(0)', /Users/anrussell/.cargo/registry/src/github.com-1ecc6299db9ec823/gfx_device_gl-0.14.5/src/lib.rs:777:12
stack backtrace:
   0: std::sys::imp::backtrace::tracing::imp::unwind_backtrace
             at src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:49
   1: std::sys_common::backtrace::_print
             at src/libstd/sys_common/backtrace.rs:69
   2: std::panicking::default_hook::{{closure}}
             at src/libstd/sys_common/backtrace.rs:58
             at src/libstd/panicking.rs:381
   3: std::panicking::default_hook
             at src/libstd/panicking.rs:397
   4: std::panicking::begin_panic
             at src/libstd/panicking.rs:577
   5: std::panicking::begin_panic
             at src/libstd/panicking.rs:538
   6: std::panicking::try::do_call
             at src/libstd/panicking.rs:522
   7: gfx_device_gl::Device::process
             at /Users/anrussell/.cargo/registry/src/github.com-1ecc6299db9ec823/gfx_device_gl-0.14.5/src/lib.rs:777
   8: gfx_device_gl::Device::unbind_target
             at /Users/anrussell/.cargo/registry/src/github.com-1ecc6299db9ec823/gfx_device_gl-0.14.5/src/lib.rs:406
   9: gfx_device_gl::Device::no_fence_submit
             at /Users/anrussell/.cargo/registry/src/github.com-1ecc6299db9ec823/gfx_device_gl-0.14.5/src/lib.rs:782
  10: gfx_device_gl::Device::track_mapped_gpu_access
             at /Users/anrussell/.cargo/registry/src/github.com-1ecc6299db9ec823/gfx_device_gl-0.14.5/src/lib.rs:906
  11: <gfx::encoder::Encoder<R, C>>::flush_no_reset
             at /Users/anrussell/.cargo/registry/src/github.com-1ecc6299db9ec823/gfx-0.16.1/src/encoder.rs:194
  12: <gfx::encoder::Encoder<R, C>>::flush
             at /Users/anrussell/.cargo/registry/src/github.com-1ecc6299db9ec823/gfx-0.16.1/src/encoder.rs:185
  13: <piston_window::PistonWindow<W>>::draw_2d
             at /Users/anrussell/.cargo/registry/src/github.com-1ecc6299db9ec823/piston_window-0.73.0/src/lib.rs:227
  14: multi_window::main
             at src/multi_window.rs:21
  15: panic_unwind::dwarf::eh::read_encoded_pointer
             at src/libpanic_unwind/lib.rs:99
  16: <std::rand::reader::ReaderRng<R> as rand::Rng>::fill_bytes
             at src/libstd/panicking.rs:459
             at src/libstd/panic.rs:361
             at src/libstd/rt.rs:59
  17: multi_window::main::{{closure}}

[bvssvni]

I get the same error on OSX 10.11.6.