Fix for bug #5513: FIND_IN_SET fails if set ends with a comma

mysql-test/r/func_set.result

@@ -64,3 +64,6 @@ find_in_set('a',binary 'A,B,C')
 select find_in_set(binary 'a', 'A,B,C');
 find_in_set(binary 'a', 'A,B,C')
 0
+select find_in_set('1','3,1,');
+find_in_set('1','3,1,')
+2

mysql-test/t/func_set.test

@@ -47,3 +47,8 @@ select find_in_set(binary 'a',binary 'A,B,C');
 select find_in_set('a',binary 'A,B,C');
 select find_in_set(binary 'a', 'A,B,C');
 
+#
+# Bug5513:FIND_IN_SET fails if set ends with a comma
+#
+select find_in_set('1','3,1,');
+

sql/item_func.cc

@@ -1455,10 +1455,11 @@ longlong Item_func_find_in_set::val_int()
       {
         const char *substr_end= str_end + symbol_len;
         bool is_last_item= (substr_end == real_end);
-        if (wc == (my_wc_t) separator || is_last_item)
+        bool is_separator= (wc == (my_wc_t) separator);
+        if (is_separator || is_last_item)
         {
           position++;
-          if (is_last_item)
+          if (is_last_item && !is_separator)
             str_end= substr_end;
           if (!my_strnncoll(cs, (const uchar *) str_begin,
                             str_end - str_begin,