Display filter expressions where the protocol name starts with digit and contains a hyphen are rejected

Summary

Entering a display filter expression where the protocol name starts with a digit and contains a hyphen is rejected. This effects the protocols:

• 5co-legacy
• 5co-rap

Steps to reproduce

Open the Display Filter Expression dialog from the Analyze menu and select any of the protocols listed above. In no way an accepted expression can be created. The same happens when entering these expressions in the display filter toolbar.

What is the current bug behavior?

Display filter expression is rejected.

What is the expected correct behavior?

Display filter expression is accepted, if valid.

Relevant logs and/or screenshots

Build information

Version 4.2.0 (v4.2.0-0-g54eedfc63953).

Compiled (64-bit) using Clang 14.0.3 (clang-1403.0.22.14.1), with GLib 2.68.4,
with Qt 6.2.4, with libpcap, without POSIX capabilities, with zlib 1.2.11, with
PCRE2, with Lua 5.2.4, with GnuTLS 3.7.8 and PKCS #11 support, with Gcrypt
1.10.2, with Kerberos (MIT), with MaxMind, with nghttp2 1.56.0, with nghttp3
0.15.0, with brotli, with LZ4, with Zstandard, with Snappy, with libxml2 2.11.5,
with libsmi 0.4.8, with QtMultimedia, with automatic updates using Sparkle, with
Minizip, with binary plugins.

Running on macOS 14.1.1, build 23B81 (Darwin 23.1.0), with Apple M1, with 16384
MB of physical memory, with GLib 2.68.4, with Qt 6.2.4, with libpcap 1.10.1,
with zlib 1.2.12, with PCRE2 10.39 2021-10-29, with c-ares 1.19.1, with GnuTLS
3.7.8, with Gcrypt 1.10.2, with nghttp2 1.56.0, with nghttp3 0.15.0, with brotli
1.0.9, with LZ4 1.9.4, with Zstandard 1.4.5, with libsmi 0.4.8, with light
display mode, with mixed DPI, with QPA plugin "cocoa", with LC_TYPE=C, binary
plugins supported.