sql_show.cc during rqg_info_schema test on Windows".

Ensure we do not access freed memory when filling
information_schema.views when one of the views
could not be properly opened.



mysql-test/r/information_schema.result:
  Update results - a fix for Bug#56540.
mysql-test/t/information_schema.test:
  Add a test case for Bug#56540
sql/sql_base.cc:
  Push an error into the Diagnostics area
  when we return an error.
  This directs get_all_tables() to the execution
  branch which doesn't involve 'process_table()'
  when no table/view was opened.
sql/sql_show.cc:
  Do not try to access underlying table fields
  when opening of a view failed. The underlying
  table is closed in that case, and accessing
  its fields may lead to dereferencing a damaged 
  pointer.