lp:737474 Wrong result with DAY(COALESCE(NULL)) in 5.1-micro

fix the return value of Item_func_coalesce::get_date()

mysql-test/r/func_time.result

@@ -1533,3 +1533,6 @@ select least(greatest(f3, f2, f4), f5) from t1;
 least(greatest(f3, f2, f4), f5)
 0000-00-00 00:00:00
 drop table t1;
+select day(coalesce(null));
+day(coalesce(null))
+NULL

mysql-test/t/func_time.test

@@ -968,3 +968,8 @@ insert ignore t1 values ('04:38:11','0000-00-00 00:00:00',0,'0000-00-00 00:00:00
 select least(greatest(f3, f2, f4), f5) from t1;
 drop table t1;
 
+#
+# lp:737474 Wrong result with DAY(COALESCE(NULL)) in 5.1-micro
+#
+select day(coalesce(null));
+

sql/item_cmpfunc.cc

@@ -2917,7 +2917,7 @@ bool Item_func_coalesce::get_date(MYSQL_TIME *ltime,uint fuzzydate)
       return res;
   }
   null_value=1;
-  return 0;
+  return 1;
 }