Bug#25197 repeat function returns null when using table field directly as count

 - Add extra test case from bug#27073
 - Change "if" to be optimized for count > 0


mysql-test/r/func_str.result:
  Add test case from bug#27073
mysql-test/t/func_str.test:
  Add test case from bug#27073
sql/item_strfunc.cc:
  Change the if statemnet to be optimized for the normal case where count > 0

mysql-test/r/func_str.result

@@ -1953,5 +1953,14 @@ A	B	tire
 		0
 #	#	1
 ##	##	2
+SELECT REPEAT('0', CAST(0 AS UNSIGNED));
+REPEAT('0', CAST(0 AS UNSIGNED))
+
+SELECT REPEAT('0', -2);
+REPEAT('0', -2)
+
+SELECT REPEAT('0', 2);
+REPEAT('0', 2)
+00
 DROP TABLE t1;
 End of 5.0 tests

mysql-test/t/func_str.test

@@ -1028,6 +1028,10 @@ INSERT INTO `t1` (`id`, `tire`) VALUES ('A', 0), ('B', 1),('C', 2);
 SELECT REPEAT( '#', tire ) AS A,
        REPEAT( '#', tire % 999 ) AS B, tire FROM `t1`;
 
+SELECT REPEAT('0', CAST(0 AS UNSIGNED));
+SELECT REPEAT('0', -2);
+SELECT REPEAT('0', 2);
+
 DROP TABLE t1;
 
 --echo End of 5.0 tests

sql/item_strfunc.cc

@@ -2252,7 +2252,7 @@ String *Item_func_repeat::val_str(String *str)
     goto err;				// string and/or delim are null
   null_value= 0;
 
-  if (count == 0 || count < 0 && !args[1]->unsigned_flag)
+  if (count <= 0 && (count == 0 || !args[1]->unsigned_flag))
     return &my_empty_string;
 
   /* Assumes that the maximum length of a String is < INT_MAX32. */