Expression list with four or more expressions in a 'for' loop can crash the interpreter.

Fetch from: https://www.lua.org/bugs.html#5.3.3-1

Signed-off-by: Francois Perrad <francois.perrad@gadz.org>

--- a/src/lparser.c
+++ b/src/lparser.c
@@ -323,6 +323,8 @@
       luaK_nil(fs, reg, extra);
     }
   }
+  if (nexps > nvars)
+    ls->fs->freereg -= nexps - nvars;  /* remove extra values */
 }
 
 
@@ -1160,11 +1162,8 @@
     int nexps;
     checknext(ls, '=');
     nexps = explist(ls, &e);
-    if (nexps != nvars) {
+    if (nexps != nvars)
       adjust_assign(ls, nvars, nexps, &e);
-      if (nexps > nvars)
-        ls->fs->freereg -= nexps - nvars;  /* remove extra values */
-    }
     else {
       luaK_setoneret(ls->fs, &e);  /* close last expression */
       luaK_storevar(ls->fs, &lh->v, &e);
--