Better error message if calling yabai failed

Used to just print:
```
** Warning:   LuaSkin: hs.task:launch() Unable to launch hs.task process: launch path not accessible
```

Now it prints the full command it was trying to run:

```
query: Error calling '/usr/local/bin/yabai -m query --windows'. Please check logs above this message to find out what went wrong.
```

stackline/query.lua

@@ -5,12 +5,19 @@ local function yabai(command, callback) -- {{{
  callback = callback or function(x) return x end
  command = '-m ' .. command
 
- hs.task.new(
-  stackline.config:get'paths.yabai',
-  u.task_cb(callback), -- wrap callback in json decoder
-  command:split(' ')
+ local task = hs.task.new(
+ stackline.config:get 'paths.yabai',
+ u.task_cb(callback),  -- wrap callback in json decoder
+ command:split(' ')
  ):start()
-end -- }}}
+ if not task then
+ log.e(
+ "Error calling '" ..
+ stackline.config:get('paths.yabai') ..
+ " " .. command .. "'. " .. "Please check logs above this message to find out what went wrong."
+ )
+ end
+ end -- }}}
 
 local function stackIdMapper(yabaiWindow) -- {{{
  -- u.p(yabaiWindow)