steam fails to start if LD_LIBRARY_PATH is unbound when STEAM_RUNTIME=0

[Desert Hobo]

On linux, using today's latest steam client (1422669294), when STEAM_RUNTIME=0, steam fails to launch if LD_LIBRARY_PATH is unbound (unset):
---
>steam
Running Steam on arch rolling 64-bit
STEAM_RUNTIME is disabled by the user
/home/ademers/.local/share/Steam/steam.sh: line 713: LD_LIBRARY_PATH: unbound variable
---

However, if STEAM_RUNTIME=1, then it starts. Comparing the different paths used between STEAM_RUNTIME=1 and =0 indicates that, on line 713, the following should be replaced:
# Need to add /usr/lib32 to the library path to pick up libvdpau_nvidia.so on Ubuntu 12.04
- export LD_LIBRARY_PATH="$LD_LIBRARY_PATH:/usr/lib32"
+ export LD_LIBRARY_PATH="${LD_LIBRARY_PATH-}:/usr/lib32"

This way, if LD_LIBRARY_PATH is unbound, instead of failing, it will be correctly resolved as empty, thus giving the same thing as:
export LD_LIBRARY_PATH=":/usr/lib32"

Everything is clearly described at the following link: http://wiki.bash-hackers.org/syntax/pe#use_a_default_value


As a workaround for now, a user can set LD_LIBRARY_PATH in his variables loaded at login so it is only empty (instead of unset) or manually export LD_LIBRARY_PATH.