solving null pointer exception for cross-schema FK dump, with not all sc...

...hema's mentioned

Exception happened on line 519 in DumpClient#findOrCreateTable()

Removed the pending deck from this method,  which was the indirect cause. It was useless since we forbid dumping cross-schema grouping foreign keys. Moved the check for this upward to maintain nice error message.
The current usage is really about not finding a Schema, opposed to all dump problems. Perhaps SchemaNotSelectedException would be clearer and then getMessage2() could be getSchema() instead.