I also have this error (blank welcome and blank software boutique) on a box running 32 bit arm multicore. I ran the terminal command above and got this output:
[Welcome] Starting in Software Boutique mode.
pcilib: Cannot open /proc/bus/pci
lspci: Cannot find any working access method.
Exception in thread Thread-2:
Traceback (most recent call last):
File “/usr/lib/python3.5/threading.py”, line 914, in _bootstrap_inner
File “/usr/lib/python3.5/threading.py”, line 862, in run
File “/usr/bin/ubuntu-mate-welcome”, line 1749, in detect_graphics
self.graphics_grep = self.graphics_grep.split("controller: ",1)
IndexError: list index out of range
There is no PCI bus on my machine. A possible suggestion is that some code is trying to figure out what my graphics card is and is (perhaps) querying PCI bus to find out. I am a bit new to this and so it may be a red herring. Anyway, I got the above errors when attempting to run from terminal command mode. Any help would be greatly appreciated.