Fix uninitialized argument value detected by clang CI

[ghost]

Your checklist for this pull request

• I've read the guidelines for contributing to this repository
• I made sure to follow the project's coding style
• I've added tests that prove my fix is effective or that my feature works (if possible)
• I've updated the documentation and the rizin book with the relevant information (if needed)

Detailed description
The gdb code is really strange. I don't understand how it worked.
I fixed the warning when I prevent the token processing if j != 4.

PS: Should we move shlr/gdb and shlr/tcc to subprojects?

Test plan

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Closing issues

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[XVilka]

1. There is no need to move shlr/gdb to subprojects since it's originally written for Radare2 and not used anywhere else, it's not an external library.
2. shlr/tcc shouldn't be a subproject since it contains a lot of the custom changes to the TinyCC code and should stay as is until conversion to Tree-Sitter is done. See also Enumerate all third-party code and libraries used in Rizin #209
3. We really need to run GDB tests on CI, see also [WIP] Fix gdbserver test read packet failure #535

[codecov-io]

Codecov Report

Merging #661 (c02861c) into dev (0d5e708) will decrease coverage by 0.01%.
The diff coverage is 75.00%.

@@            Coverage Diff             @@
##              dev     #661      +/-   ##
==========================================
- Coverage   42.79%   42.78%   -0.02%     
==========================================
  Files         869      869              
  Lines      316347   316346       -1     
==========================================
- Hits       135382   135334      -48     
- Misses     180965   181012      +47     

Impacted Files	Coverage Δ
librz/socket/run.c	23.72% <0.00%> (ø)
librz/bin/mangling/microsoft_demangle.c	73.76% <100.00%> (+0.02%)	⬆️
librz/core/canalysis.c	64.84% <100.00%> (ø)
shlr/gdb/src/gdbclient/responses.c	15.03% <0.00%> (-18.43%)	⬇️
librz/debug/p/debug_gdb.c	48.19% <0.00%> (-12.14%)	⬇️
librz/reg/reg.c	77.77% <0.00%> (-5.26%)	⬇️
shlr/gdb/src/gdbclient/core.c	37.51% <0.00%> (-1.97%)	⬇️
librz/core/cmd_debug.c	27.25% <0.00%> (+0.06%)	⬆️
librz/debug/p/native/linux/linux_debug.c	48.66% <0.00%> (+0.15%)	⬆️
librz/util/sys.c	60.77% <0.00%> (+0.22%)	⬆️
... and 9 more

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