-- Refined the compilation of the XQuery construct if-then-else:    We now link the LOOP relation of the then and else branches to a new rowid    operator (translation now looks like a for-loop). This forces e.g., nested    node constructors to link to the new rowid operator and allows the rewrite    engine to remove the previously linked rowid operator more easily.
-- Refined the compilation of the XQuery construct if-then-else:
   We now link the LOOP relation of the then and else branches to a new rowid
   operator (translation now looks like a for-loop). This forces e.g., nested
   node constructors to link to the new rowid operator and allows the rewrite
   engine to remove the previously linked rowid operator more easily.

-- Added some error checks for XPath location steps

zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb