webconfig: separate arguments to abbr

`abbr` used to take a single argument and split in on the first space,
but 309e10e7 and predecessors altered this behaviour. Update the web
config use of abbr to the newer format.

Fixes #3620.

share/tools/web_config/webconfig.py

@@ -842,10 +842,10 @@ class FishConfigHTTPRequestHandler(SimpleHTTPServer.SimpleHTTPRequestHandler):
             return True
 
     def do_save_abbreviation(self, abbreviation):
-        out, err = run_fish_cmd('abbr --add \'%s %s\'' % (
+        out, err = run_fish_cmd('abbr --add \'%s\' \'%s\'' % (
             abbreviation['word'], abbreviation['phrase']))
-        if err:
-            return err
+        if out or err:
+            return out
         else:
             return True