view.window() may be None during on_post_save_async
I renamed a file with AdvancedNewFile's "rename" command and observed the following in my console:

```
Traceback (most recent call last):
  File "/opt/sublime_text/sublime_plugin.py", line 487, in on_post_save_async
    callback.on_post_save_async(v)
  File "/home/fichte/.config/sublime-text-3/Packages/SublimeLinter/sublime_linter.py", line 136, in on_post_save_async
    if view.window().project_file_name() == view.file_name():
AttributeError: 'NoneType' object has no attribute 'project_file_name'
```
diff --git a/sublime_linter.py b/sublime_linter.py
index 7261223..c142961 100644
--- a/sublime_linter.py
+++ b/sublime_linter.py
@@ -133,7 +133,7 @@ class BackendController(sublime_plugin.EventListener):
             return
 
         # check if the project settings changed
-        if view.window().project_file_name() == view.file_name():
+        if view.window() and view.window().project_file_name() == view.file_name():
             lint_all_views()
             return
 
['sublime_linter.py']