Do not call clang-format if buffer is empty.

closes #102

Signed-off-by: Wolfgang E. Sanyer <WolfgangSanyer@Google.com>

Author: ezzieyguywuf

autoload/codefmt/clangformat.vim

@@ -171,7 +171,7 @@ function! codefmt#clangformat#GetFormatter() abort
     let l:result = maktaba#syscall#Create(l:cmd).WithStdin(l:input).Call()
     let l:formatted = split(l:result.stdout, "\n")
 
-    if l:supports_cursor
+    if l:supports_cursor && !(line('$') == 1 && getline(1) == '')
       " With -cursor, the first line is a JSON object.
       let l:header = remove(l:formatted, 0)
       call maktaba#buffer#Overwrite(1, line('$'), l:formatted)
@@ -182,8 +182,8 @@ function! codefmt#clangformat#GetFormatter() abort
         let [l:new_line, l:new_col] = s:OffsetToPosition(l:offset, l:formatted)
         call cursor(l:new_line, l:new_col)
       catch
-        call maktaba#error#Warn('Unable to parse clang-format cursor pos: %s',
-            \ v:exception)
+        call maktaba#error#Warn(v:exception)
+        call maktaba#error#Warn("  Unable to parse clang-formon cursor position")
       endtry
     else
       call maktaba#buffer#Overwrite(1, line('$'), l:formatted)