netcardconfig: don't fail with bash >=4.4 when scanning for networks

netcardconfig: don't fail with bash >=4.4 when scanning for networks

There was a behavior change in bash 4.4:

| % bash --version | head -1
| GNU bash, version 4.3.30(1)-release (x86_64-pc-linux-gnu)
| % cat foo
| printf "1\n2\n3\n" > /tmp/input
| i=0
| while read line
| do
| WARRAY[i++]=$line
| done < /tmp/input
| echo ${WARRAY[@] }
| % bash ./foo
| 1 2 3
| %
|
| % bash --version | head -1
| GNU bash, version 4.4.5(1)-release (x86_64-pc-linux-gnu)
| % bash ./foo
| ./foo: line 7: ${WARRAY[@] }: bad substitution
| %

While at it don't hide empty and hidden ESSIDs, this is breaking
the dialog option parsing, so while it's not really nice from
a user perspective it's still better than a failing netcardconfig.

Closes grml/release-planning#13 @ GH