Fix: Don't error on untracked files with blame

Fixes #123

lua/gitsigns.lua

@@ -749,7 +749,7 @@ end
 local _current_line_blame = void_async(function()
    local bufnr = current_buf()
    local bcache = cache[bufnr]
-   if not bcache then
+   if not bcache or not bcache.object_name then
       return
    end
 

lua/gitsigns/git.lua

@@ -195,6 +195,10 @@ M.run_blame = a.wrap(function(
       end,
       on_exit = function()
          local ret = {}
+         if #results == 0 then
+            callback({})
+            return
+         end
          local header = vim.split(table.remove(results, 1), ' ')
          ret.sha = header[1]
          ret.abbrev_sha = string.sub(ret.sha, 1, 8)

teal/gitsigns.tl

@@ -749,7 +749,7 @@ end
 local _current_line_blame = void_async(function()
   local bufnr = current_buf()
   local bcache = cache[bufnr]
-  if not bcache then
+  if not bcache or not bcache.object_name then
     return
   end
 

teal/gitsigns/git.tl

@@ -195,6 +195,10 @@ M.run_blame = a.wrap(function(
     end,
     on_exit = function()
       local ret: {string:any} = {}
+      if #results == 0 then
+        callback({})
+        return
+      end
       local header = vim.split(table.remove(results, 1), ' ')
       ret.sha = header[1]
       ret.abbrev_sha = string.sub(ret.sha as string, 1, 8)

test/gitsigns_spec.lua

@@ -436,6 +436,22 @@ describe('gitsigns', function()
     end)
   end)
 
+  describe('current line blame', function()
+    it('doesn\'t error on untracked files', function()
+      command("set updatetime=1")
+      init(true)
+      screen:detach()
+      screen:attach({ext_messages=true})
+      config.current_line_blame = true
+      exec_lua('gs.setup(...)', config)
+      sleep(20)
+      edit(newfile)
+      feed("iline<esc>")
+      command("write")
+      screen:expect{messages = { { content = { { "<" } }, kind = "" } } }
+    end)
+  end)
+
   local function testsuite(advanced_features)
     return function()
       before_each(function()