Arguments do not work as expected

Proton 5.0-1
OS: Linux

I am doing some testing on the Proton script. And found that, when the line

self.run_proc([g_proton.wine_bin, "steam"] + sys.argv[2:] + self.cmdlineappend)

is invoked, if the sys.argv[2:] is more than one argument, then the process doesn't run. This is not happening in 4.11-2 version.

Looks like the steam argument after wine (g_proton.wine_bin) causes the issue in 5.0-1. Removing the steam, then the process can run with argument.

Steps to re-produce

1. Create a directory /tmp/proton_test
2. Run the following script,

#!/bin/bash

export STEAM_COMPAT_DATA_PATH="/tmp/proton_test"
export WINEPREFIX="/tmp/proton_test/pfx"
export PATH="$HOME/.steam/steam/steamapps/common/Proton 5.0/dist/bin:$PATH"
export LD_LIBRARY_PATH="$HOME/.steam/steam/steamapps/common/Proton 5.0/dist/lib:$HOME/.steam/steam/steamapps/common/Proton 5.0/dist/lib64:$LD_LIBRARY_PATH"
export WINEDLLPATH="$HOME/.steam/steam/steamapps/common/Proton 5.0/dist/lib/wine/fakedlls:$HOME/.steam/steam/steamapps/common/Proton 5.0/dist/lib64/wine/fakedlls"

"$HOME/.steam/steam/steamapps/common/Proton 5.0/proton" run notepad test.txt

3. Nothing shown.

If change to Proton 4.11, the test.txt will be open by notepad.

Start at the Proton script's run_proc invocation shown in the report and compare its argument handling with Proton 4.11-2. Reproduce the provided /tmp/proton_test command with multiple arguments, then verify that Proton 5.0-1 launches notepad and opens test.txt as expected.