Error detected while processing function jedi#usages[2]..jedi#clear_usage

### Issue

When trying to use Ctrl-G to get usages of functions, I get an "Error detected while processing function jedi#usages[2]..jedi#clear_usages"

```
"~\XPlane2Blender\io_xplane2blender\xplane_helpers.py" [unix] 432L, 16958C
Error detected while processing function jedi#usages[2]..jedi#clear_usages:
line 21:
Traceback (most recent call last):
File "", line 1, in
File "C:\Users\Ted\.vim\bundle\jedi-vim\pythonx\jedi_vim.py", line 558, in clear_usages
'bufnr': buf.number,
vim.error: Vim:E119: Not enough arguments for function: prop_remove
```

### Steps to reproduce
I can make it happen regularly, but not always with the same function.

- Go to some identifier for a function
- Press CTRL-G
- Somes this error pops up and the results aren't shown.
- I think it may not be finding the whole usages across the project when it does work either, but, that'll be a separate bug if found.

myvimrc:
```
set nocompatible

let script_dir = fnamemodify(expand(''), ':h')
let &runtimepath .= ','.script_dir.','.script_dir.'/after'

" Put your config changes here.
" let g:jedi#show_call_signatures=1

let g:jedi#completions_enabled = 1

let g:jedi#popup_on_dot = 1
let g:jedi#popup_select_first = 0
let g:jedi#use_tabs_not_buffers = 0

let g:jedi#auto_vim_configuration = 0
let g:jedi#auto_initialization = 1

"Jedi Commands
let g:jedi#completions_command = ""
let g:jedi#goto_command = "gd"
let g:jedi#documentation_command = "K"
let g:jedi#rename_command = "rn"
let g:jedi#usages_command = ""

let g:jedi#show_call_signatures = 1
let g:jedi#show_call_signatures_delay = 500

call jedi#configure_call_signatures()
syntax on
filetype plugin indent on
```

### Output of “:verbose JediDebugInfo”
#### Jedi-vim debug information

##### jedi-vim version

- jedi-vim git version: 0.10.0-8-g08f13af
- jedi git submodule status: 005f69390c4b1a3b864e7373cfcbdaf95e65411d pythonx/jedi (v0.15.1)
- parso git submodule status: c0ace63a6905500e18d8ac06af1a0a9057e63498 pythonx/parso (v0.5.1)

##### Global Python

Using Python version 3 to access Jedi.
- global sys.executable: `C:\Vim\vim81\gvim.exe`
- global sys.version: `3.7.0 (default, Aug 26 2018, 16:05:01) [MSC v.1900 64 bit (AMD64)]`
- global site module: `C:\Users\Ted\utils\programming\Python37\Lib\site.py`

##### Jedi

- path: `C:\Users\Ted\.vim\bundle\jedi-vim\pythonx\jedi\jedi\__init__.py`
- version: 0.15.1

##### Jedi environment:

- executable: C:\Users\Ted\utils\programming\Python37\python.exe
- sys_path:
- `C:\Users\Ted\utils\programming\Python37\python37.zip`
- `C:\Users\Ted\utils\programming\Python37\DLLs`
- `C:\Users\Ted\utils\programming\Python37\lib`
- `C:\Users\Ted\utils\programming\Python37`
- `C:\Users\Ted\utils\programming\Python37\lib\site-packages`

##### Known environments

- (C:\Users\Ted\utils\programming\Python37\python.exe)

- (C:\Users\Ted\utils\programming\Python36\python.exe)

##### Settings

```
g:jedi#popup_select_first = 0 (default: 1)
g:jedi#usages_command = '' (default: 'n')
g:jedi#completions_command = '' (default: '')
g:jedi#rename_command = 'rn' (default: 'r')
g:jedi#auto_vim_configuration = 0 (default: 1)
g:jedi#goto_command = 'gd' (default: 'd')

omnifunc=jedi#completions
Last set from ~\.vim\bundle\jedi-vim\autoload\jedi.vim line 740
completeopt=menu,preview
```

#### :version
```

VIM - Vi IMproved 8.1 (2018 May 18, compiled Dec 19 2018 20:33:53)
MS-Windows 64-bit GUI version with OLE support
Included patches: 1-608
Compiled by micbou
Huge version with GUI. Features included (+) or not (-):
+acl +cindent +cursorshape +farsi +jumplist +mksession +path_extra +ruby/dyn +tcl/dyn +vartabs +writebackup
+arabic +clientserver +dialog_con_gui +file_in_path +keymap +modify_fname +perl/dyn +scrollbind -termguicolors +vertsplit -xfontset
+autocmd +clipboard +diff +find_in_path +lambda +mouse +persistent_undo +signs +terminal +virtualedit -xim
+autochdir +cmdline_compl +digraphs +float +langmap +mouseshape -postscript +smartindent -termresponse +visual +xpm_w32
+autoservername +cmdline_hist +directx +folding +libcall +multi_byte_ime/dyn +printer +startuptime +textobjects +visualextra -xterm_save
+balloon_eval +cmdline_info -dnd -footer +linebreak +multi_lang +profile +statusline +textprop +viminfo
-balloon_eval_term +comments -ebcdic +gettext/dyn +lispindent +mzscheme/dyn +python/dyn -sun_workshop -tgetent +vreplace
+browse +conceal +emacs_tags -hangul_input +listcmds +netbeans_intg +python3/dyn +syntax +timers -vtp
++builtin_terms +cryptv +eval +iconv/dyn +localmap +num64 +quickfix +tag_binary +title +wildignore
+byte_offset +cscope +ex_extra +insert_expand +lua/dyn +ole +reltime +tag_old_static +toolbar +wildmenu
+channel +cursorbind +extra_search +job +menu +packages +rightleft -tag_any_white +user_commands +windows
system vimrc file: "$VIM\vimrc"
user vimrc file: "$HOME\_vimrc"
2nd user vimrc file: "$HOME\vimfiles\vimrc"
3rd user vimrc file: "$VIM\_vimrc"
user exrc file: "$HOME\_exrc"
2nd user exrc file: "$VIM\_exrc"
system gvimrc file: "$VIM\gvimrc"
user gvimrc file: "$HOME\_gvimrc"
2nd user gvimrc file: "$HOME\vimfiles\gvimrc"
3rd user gvimrc file: "$VIM\_gvimrc"
defaults file: "$VIMRUNTIME\defaults.vim"
system menu file: "$VIMRUNTIME\menu.vim"
Compilation: cl -c /W3 /nologo -I. -Iproto -DHAVE_PATHDEF -DWIN32 -DFEAT_CSCOPE -DFEAT_TERMINAL -DFEAT_NETBEANS_INTG -DFEAT_JOB_CHANNEL -DFEAT_XPM_W32 -DWINVER=0x0501 -D_WIN32_WINNT=0x0501 /MP -DHAVE_STDINT_H /Ox /GL -DNDEBUG /MD -DFEAT_OLE -DFEAT_MBYTE_IME -DDYNAMIC_IME -DGLOBAL_IME -DFEAT_MBYTE -DFEAT_GUI_W32 -DFEAT_DIRECTX -DDYNAMIC_DIRECTX -DFEAT_DIRECTX_COLOR_EMOJI -DDYNAMIC_ICONV -DDYNAMIC_GETTEXT -DFEAT_TCL -DDYNAMIC_TCL -DDYNAMIC_TCL_DLL=\"tcl86t.dll\" -DDYNAMIC_TCL_VER=\"8.6\" -DFEAT_LUA -DDYNAMIC_LUA -DDYNAMIC_LUA_DLL=\"lua53.dll\" -DFEAT_PYTHON -DDYNAMIC_PYTHON -DDYNAMIC_PYTHON_DLL=\"python27.dll\" -DFEAT_PYTHON3 -DDYNAMIC_PYTHON3 -DDYNAMIC_PYTHON3_DLL=\"python37.dll\" -DFEAT_MZSCHEME -I "C:\Racket\include" -DMZ_PRECISE_GC -DDYNAMIC_MZSCHEME -DDYNAMIC_MZSCH_DLL=\"libracket3m_bkrfgg.dll\" -DDYNAMIC_MZGC_DLL=\"libracket3m_bkrfgg.dll\" -DFEAT_PERL -DPERL_IMPLICIT_CONTEXT -DPERL_IMPLICIT_SYS -DDYNAMIC_PERL -DDYNAMIC_PERL_DLL=\"perl526.dll\" -DFEAT_RUBY -DDYNAMIC_RUBY -DDYNAMIC_RUBY_VER=25 -DDYNAMIC_RUBY_DLL=\"x64-msvcrt-ruby250.dll\" -DFEAT_HUGE /Fd.\ObjGXOULYHTRZAMD64/ /Zi
Linking: link /nologo /subsystem:windows /opt:ref /LTCG:STATUS /HIGHENTROPYVA:NO oldnames.lib kernel32.lib advapi32.lib shell32.lib gdi32.lib comdlg32.lib ole32.lib netapi32.lib uuid.lib /machine:AMD64 gdi32.lib version.lib winspool.lib comctl32.lib advapi32.lib shell32.lib netapi32.lib /machine:AMD64 msvcrt.lib oleaut32.lib user32.lib /nodefaultlib:lua53.lib /STACK:8388608 /nodefaultlib:python27.lib /nodefaultlib:python37.lib "C:\ActiveTcl\lib\tclstub86.lib" WSock32.lib xpm\x64\lib-vc14\libXpm.lib /PDB:gvim.pdb -debug
```

#### :messages
```
E492: Not an editor command: MRU
"~\XPlane2Blender\io_xplane2blender\tests\test_creation_helpers.py" [unix] 736L, 27556C
search hit BOTTOM, continuing at TOP
E486: Pattern not found: exportable_collections
search hit BOTTOM, continuing at TOP
"~\XPlane2Blender\io_xplane2blender\xplane_helpers.py" [unix] 432L, 16958C
Error detected while processing function jedi#usages[2]..jedi#clear_usages:
line 21:
Traceback (most recent call last):
File "", line 1, in
File "C:\Users\Ted\.vim\bundle\jedi-vim\pythonx\jedi_vim.py", line 558, in clear_usages
'bufnr': buf.number,
vim.error: Vim:E119: Not enough arguments for function: prop_remove
```

:scriptnames

```
1: ~\.vim\bundle\jedi-vim\minimal.vimrc
2: ~\.vim\bundle\jedi-vim\autoload\jedi.vim
3: C:\Vim\vim81\syntax\syntax.vim
4: C:\Vim\vim81\syntax\synload.vim
5: C:\Vim\vim81\syntax\syncolor.vim
6: C:\Vim\vim81\filetype.vim
7: C:\Vim\vim81\menu.vim
8: C:\Vim\vim81\autoload\paste.vim
9: C:\Vim\vim81\ftplugin.vim
10: C:\Vim\vim81\indent.vim
11: C:\Vim\vim81\plugin\getscriptPlugin.vim
12: C:\Vim\vim81\plugin\gzip.vim
13: C:\Vim\vim81\plugin\logiPat.vim
14: C:\Vim\vim81\plugin\manpager.vim
15: C:\Vim\vim81\plugin\matchparen.vim
16: C:\Vim\vim81\plugin\netrwPlugin.vim
17: C:\Vim\vim81\plugin\rrhelper.vim
18: C:\Vim\vim81\plugin\spellfile.vim
19: C:\Vim\vim81\plugin\tarPlugin.vim
20: C:\Vim\vim81\plugin\tohtml.vim
21: C:\Vim\vim81\plugin\vimballPlugin.vim
22: C:\Vim\vim81\plugin\zipPlugin.vim
23: ~\.vim\bundle\jedi-vim\plugin\jedi.vim
24: C:\Vim\vim81\syntax\python.vim
25: ~\.vim\bundle\jedi-vim\after\syntax\python.vim
26: C:\Vim\vim81\ftplugin\python.vim
27: ~\.vim\bundle\jedi-vim\ftplugin\python\jedi.vim
28: ~\.vim\bundle\jedi-vim\after\ftplugin\python\jedi.vim
29: C:\Vim\vim81\indent\python.vim
30: C:\Vim\vim81\syntax\qf.vim
31: C:\Vim\vim81\ftplugin\qf.vim
```