fallback to fzf plugin if not installed globally (closes #383)

lua/fzf-lua/config.lua

@@ -768,6 +768,13 @@ function M.normalize_opts(opts, defaults)
      not executable(opts.fzf_bin, utils.warn, "fallback to 'fzf'.") then
     -- default|fallback to fzf
     opts.fzf_bin = "fzf"
+    -- try fzf plugin if fzf is not installed globally
+    if vim.fn.executable(opts.fzf_bin) ~= 1 then
+      local ok, fzf_plug = pcall(vim.api.nvim_call_function, "fzf#exec", {})
+      if ok and fzf_plug then
+        opts.fzf_bin = fzf_plug
+      end
+    end
     if not executable(opts.fzf_bin, utils.err,
       "aborting. Please make sure 'fzf' is in installed.") then
       return nil

lua/fzf-lua/core.lua

@@ -52,6 +52,7 @@ M.fzf = function(opts, contents)
   -- normalize with globals if not already normalized
   if not opts._normalized then
     opts = config.normalize_opts(opts, {})
+    if not opts then return end
   end
   if opts.fn_pre_win then
     opts.fn_pre_win(opts)