Addition to fix for bug#10974. Fixed spelling.

sql/share/errmsg.txt

@@ -3813,7 +3813,7 @@ ER_WRONG_MRG_TABLE
 	cze "V-Bechny tabulky v MERGE tabulce nejsou definovny stejn"
 	dan "Tabellerne i MERGE er ikke defineret ens"
 	nla "Niet alle tabellen in de MERGE tabel hebben identieke gedefinities"
-	eng "Unable to open underlying table which is differently defined or of non-MyISAM type or doesn't exists"
+	eng "Unable to open underlying table which is differently defined or of non-MyISAM type or doesn't exist"
 	est "Kik tabelid MERGE tabeli mratluses ei ole identsed"
 	fre "Toutes les tables de la table de type MERGE n'ont pas la mme dfinition"
 	ger "Nicht alle Tabellen in der MERGE-Tabelle sind gleich definiert"