Yosys crash when module output signal name same as module name

### Version Yosys 0.66+70 (git sha1 8eb313307, Release, Clang /usr/bin/clang++ 18.1.8) ### On which OS did this happen? Linux ### Reproduction Steps With source: ``` module pdm #( parameter PHY = "zero" )( output wire pdm, ); if (PHY == "zero") begin assign pdm = 1'b0; end endmodule ``` and command line of: ``` yosys -p 'synth_ice40 -top pdm ' pdm.v ``` ### Expected Behavior Yosys should run to completion without crashing. ### Actual Behavior Yosys runs and then crashes with the following output: ``` 2.3. Executing AST frontend in derive mode using pre-parsed AST for module `\pdm'. Generating RTLIL representation for module `\pdm'. terminate called after throwing an instance of 'std::out_of_range' what(): basic_string::at: __n (which is 4) >= this->size() (which is 4) Aborted (core dumped) ``` This has been observed on several versions of yosys going back some time, however it is *not* seen on much older versions. Yosys 0.42+15 (git sha1 2fd2b6538, clang++ 14.0.0-1ubuntu1.1 -fPIC -Os) works fine for example.