Revert "archweb: use jq's -e flag to indicate not-found as failure"

This reverts commit b233ace while
preserving bd3f96a.

jq, even with -e, does not exit non-zero when given an empty input. This
is apparently a known feature:

jqlang/jq#1497
jqlang/jq#1142

Thus, revert this oversimplification which leads to problems when curl
fails, or otherwise returns an empty response body.

Closes #29.

archweb.inc.sh

@@ -1,4 +1,9 @@
 archweb_get_pkgbase() {
-  curl -Gs "https://www.archlinux.org/packages/search/json/" --data-urlencode "q=$1" |
-    jq -er --arg pkgname "$1" 'limit(1; .results[] | select(.pkgname == $pkgname).pkgbase)'
+  local pkgbase
+
+  pkgbase=$(curl -Gs 'https://www.archlinux.org/packages/search/json/' --data-urlencode "q=$1" |
+      jq -r --arg pkgname "$1" 'limit(1; .results[] | select(.pkgname == $pkgname).pkgbase)')
+  [[ $pkgbase ]] || return
+
+  printf '%s\n' "$pkgbase"
 }