add exists utility function

main.lua

@@ -96,6 +96,7 @@ local empty            = util.empty
 local lerp             = util.lerp
 local softchoice       = util.softchoice
 local unperturbed_rank = util.unperturbed_rank
+local exists           = util.exists
 
 local game = require("smb")
 game.overlay = cfg.enable_overlay
@@ -446,8 +447,9 @@ local function init()
         loadlevel(cfg.starting_world, cfg.starting_level)
     end
 
-    local res, err = pcall(network.load, network, cfg.params_fn)
-    if res == false then print(err) end
+    if exists(cfg.params_fn) then
+        network:load(cfg.params_fn)
+    end
 
     if cfg.es == 'xnes' then
         -- if you get an out of memory error, you can't use xNES. sorry!

util.lua

@@ -5,6 +5,7 @@ local ipairs = ipairs
 local log = math.log
 local max = math.max
 local min = math.min
+local open = io.open
 local pairs = pairs
 local random = math.random
 local select = select
@@ -162,6 +163,16 @@ local function argsort(t, comp, out)
     return out
 end
 
+local function exists(fn)
+    local f = open(fn, "r")
+    if f then
+        f:close()
+        return true
+    else
+        return false
+    end
+end
+
 return {
     signbyte=signbyte,
     boolean_xor=boolean_xor,
@@ -183,4 +194,5 @@ return {
     rchoice2=rchoice2,
     rbool=rbool,
     argsort=argsort,
+    exists=exists,
 }