Bug #48985: show create table crashes if previous access to the table was killed

When checking for an error after removing the special view error handler the code
was not taking into account that open_tables() may fail because of the current
statement being killed. 
Added a check for thd->killed.
Added a client program to test it.

mysql-test/r/show_check.result

@@ -1454,4 +1454,10 @@ GRANT PROCESS ON *.* TO test_u@localhost;
 SHOW ENGINE MYISAM MUTEX;
 SHOW ENGINE MYISAM STATUS;
 DROP USER test_u@localhost;
+#
+# Bug #48985: show create table crashes if previous access to the table
+#    was killed
+#
+SHOW CREATE TABLE non_existent;
+ERROR 70100: Query execution was interrupted
 End of 5.1 tests

mysql-test/t/show_check.test

@@ -1207,6 +1207,28 @@ connection default;
 DROP USER test_u@localhost;
 
 
+--echo #
+--echo # Bug #48985: show create table crashes if previous access to the table
+--echo #    was killed
+--echo #
+
+connect(con1,localhost,root,,);
+CONNECTION con1;
+LET $ID= `SELECT connection_id()`;
+
+CONNECTION default;
+--disable_query_log
+eval KILL QUERY $ID;
+--enable_query_log
+
+CONNECTION con1;
+--error ER_QUERY_INTERRUPTED
+SHOW CREATE TABLE non_existent;
+
+CONNECTION default;
+DISCONNECT con1;
+
+
 --echo End of 5.1 tests
 
 # Wait till all disconnects are completed

sql/sql_show.cc

@@ -719,7 +719,7 @@ mysqld_show_create(THD *thd, TABLE_LIST *table_list)
     thd->push_internal_handler(&view_error_suppressor);
     bool error= open_normal_and_derived_tables(thd, table_list, 0);
     thd->pop_internal_handler();
-    if (error && thd->main_da.is_error())
+    if (error && (thd->killed || thd->main_da.is_error()))
       DBUG_RETURN(TRUE);
   }