The property line caps its label at max-w-15 so a long key cannot crowd
out the value drawn beside it. When the value is empty there is nothing
to protect, but the cap still applied, truncating the label against
empty space.
Drop the cap when the value is blank and let the label truncate against
the node width instead. Same fix in BaseNode and ProxmoxGroupNode.
Closes#361
ha-relevant: yes
Pouzor
9bc02d61c2