Fixed bug #24987.

Made the function opt_sum_query to return HA_ERR_KEY_NOT_FOUND when
no matches were found (instead of -1 it returned prior this patch).
This changes allow us to avoid possible conflicts with return values
from user-defined handler methods which also may return -1. 
No particular test cases are provided with this fix.

sql/opt_sum.cc

@@ -68,9 +68,9 @@ static int maxmin_in_range(bool max_fl, Field* field, COND *cond);
     GROUP BY part.
 
   RETURN VALUES
-    0 No errors
-    1 if all items were resolved
-   -1 on impossible conditions
+    0                    no errors
+    1                    if all items were resolved
+    HA_ERR_KEY_NOT_FOUND on impossible conditions
     OR an error number from my_base.h HA_ERR_... if a deadlock or a lock
        wait timeout happens, for example
 */
@@ -216,7 +216,7 @@ int opt_sum_query(TABLE_LIST *tables, List<Item> &all_fields,COND *conds)
           if (error)
 	  {
 	    if (error == HA_ERR_KEY_NOT_FOUND || error == HA_ERR_END_OF_FILE)
-	      return -1;		       // No rows matching WHERE
+	      return HA_ERR_KEY_NOT_FOUND;	      // No rows matching WHERE
 	    /* HA_ERR_LOCK_DEADLOCK or some other error */
  	    table->file->print_error(error, MYF(0));
             return(error);
@@ -303,7 +303,7 @@ int opt_sum_query(TABLE_LIST *tables, List<Item> &all_fields,COND *conds)
           if (error)
           {
 	    if (error == HA_ERR_KEY_NOT_FOUND || error == HA_ERR_END_OF_FILE)
-	      return -1;		       // No rows matching WHERE
+	      return HA_ERR_KEY_NOT_FOUND;	     // No rows matching WHERE
 	    /* HA_ERR_LOCK_DEADLOCK or some other error */
  	    table->file->print_error(error, MYF(0));
             return(error);

sql/sql_select.cc

@@ -531,23 +531,25 @@ JOIN::optimize()
   {
     int res;
     /*
-      opt_sum_query() returns -1 if no rows match to the WHERE conditions,
-      or 1 if all items were resolved, or 0, or an error number HA_ERR_...
+      opt_sum_query() returns HA_ERR_KEY_NOT_FOUND if no rows match
+      to the WHERE conditions,
+      or 1 if all items were resolved,
+      or 0, or an error number HA_ERR_...
     */
     if ((res=opt_sum_query(tables_list, all_fields, conds)))
     {
+      if (res == HA_ERR_KEY_NOT_FOUND)
+      {
+	zero_result_cause= "No matching min/max row";
+	error=0;
+	DBUG_RETURN(0);
+      }
       if (res > 1)
       {
         thd->fatal_error();
         error= res;
 	DBUG_RETURN(1);
       }
-      if (res < 0)
-      {
-	zero_result_cause= "No matching min/max row";
-	error=0;
-	DBUG_RETURN(0);
-      }
       zero_result_cause= "Select tables optimized away";
       tables_list= 0;				// All tables resolved
       /*