[Fix] No longer delete missions if misn.finish() has no params. Should

fix regressions.

src/misn_lua.c

@@ -486,7 +486,6 @@ static int misn_finish(lua_State* L) {
   if(lua_isboolean(L, 1)) b = lua_toboolean(L, 1);
   else {
     lua_pushstring(L, "Mission Done");
-    misn_delete = 1;
     lua_error(L); /* THERE IS NO RETURN! */
     return 0;
   }