Better Patch for Lua 5.1.5 #2

[me the user]

https://www.lua.org/bugs.html#5.1.5-2

When loading a file, Lua may call the reader function again after it
returned end of input .
reported by Chris Howie on 05 Jun 2013. existed since 5.1. fixed in 5.2.0.
Example:

load(function () print("called"); return nil end)
--> called
--> called (should be called only once!)

The patch given adds a new variable 'eoz'
I think it should just set z->reader to NULL
and check for that condition instead

lzio.c:
@@ -22,10 +22,15 @@
size_t size;
lua_State *L = z->L;
const char *buff;
+ if (!z->reader)
+ return EOZ;
lua_unlock(L);
buff = z->reader(L, z->data, &size);
lua_lock(L);
- if (buff == NULL || size == 0) return EOZ;
+ if (buff == NULL || size == 0) {
+ z->reader = NULL; /* avoid calling reader function next time */
+ return EOZ;
+ }
z->n = size - 1;
z->p = buff;
return char2int(*(z->p++));