微调背景模块，自定义模式设置背景的时候访问不到特殊背景了

Zframework/background.lua

@@ -24,6 +24,9 @@ end
 function BG.getList()
     return BGlist
 end
+function BG.remList(name)
+    table.remove(BGlist,TABLE.find(BGlist,name))
+end
 function BG.send(...)
     if BG.event then
         BG.event(...)

main.lua

@@ -380,6 +380,7 @@ for _,v in next,fs.getDirectoryItems('parts/backgrounds')do
         BG.add(name,require('parts.backgrounds.'..name))
     end
 end
+BG.remList('none')BG.remList('gray')BG.remList('custom')
 --Load scene files from SOURCE ONLY
 for _,v in next,fs.getDirectoryItems('parts/scenes')do
     if isSafeFile('parts/scenes/'..v)then

parts/backgrounds/custom.lua

@@ -18,8 +18,10 @@ function back.resize()
 end
 function back.draw()
     gc_clear(.1,.1,.1)
-    gc_setColor(1,1,1,alpha)
-    mDraw(image,mx,my,nil,k)
+    if image then
+        gc_setColor(1,1,1,alpha)
+        mDraw(image,mx,my,nil,k)
+    end
 end
 function back.event(a,img)
     if a then alpha=a end