resty: Add workaround for new curl versions

As Mathieu found out, his new curl version won't process the empty
string being passed to curl as argument, resulting from the no-body case
for GET. The empty string was treated as additional URL which was
skipped over in the past with a warning but now it's a hard error.

resty

@@ -214,7 +214,13 @@ HELP
 
     # Forge command and display it if dry-run
     local cmd
-    cmd=(curl -sLv $curl_opt $(printf "%q" "$body") -X $method  -b \"$cookies/$domain\" -c \"$cookies/$domain\" "$(\
+    # Flatcar: Add workaround for new curl versions
+    local body_arg=()
+    body_arg=($(printf "%q" "$body"))
+    if [ "${body_arg[*]}" = "" ] || [ "${body_arg[*]}" = "''" ]; then
+        body_arg=()
+    fi
+    cmd=(curl -sLv $curl_opt "${body_arg[@]}" -X $method  -b \"$cookies/$domain\" -c \"$cookies/$domain\" "$(\
         [ -n "$curlopt_cmd" ] && printf '%s ' ${curlopt_cmd[@]})"\"$_path$query\")
     if [ "$dry_run" = "yes" ] ; then
         echo "${cmd[@]}"