fix(bash-v2): skip empty completions when filtering descriptions (#1691)

`read` gives a last null value following a trailing newline.

Regression from fb8031162c.

bash_completionsV2.go

@@ -188,6 +188,7 @@ __%[1]s_handle_standard_completion_case() {
     local compline
     # Look for the longest completion so that we can format things nicely
     while IFS='' read -r compline; do
+        [[ -z $compline ]] && continue
         # Strip any description before checking the length
         comp=${compline%%%%$tab*}
         # Only consider the completions that match