fix(startup): "nvim -l foo.lua" may not set arg0 #24161

Problem:
Using "nvim -l args.lua" without passing extra script args, does not set `_G.arg[0]`.

Steps to reproduce:
```
cat > args.lua<<EOF
vim.print(_G.arg, '')
vim.print(vim.v.argv, '')
EOF

nvim --clean -l args.lua
```

Solution:
Fix condition in command_line_scan.

src/nvim/main.c

@@ -1361,7 +1361,7 @@ static void command_line_scan(mparm_T *parmp)
           }
           parmp->luaf = argv[0];
           argc--;
-          if (argc > 0) {  // Lua args after "-l <file>".
+          if (argc >= 0) {  // Lua args after "-l <file>".
             parmp->lua_arg0 = parmp->argc - argc;
             argc = 0;
           }