ip{, 6}tables-restore: Fix for uninitialized array 'curtable'

ip{, 6}tables-restore: Fix for uninitialized array 'curtable'

When reading sufficiently malformed input, parser might hit end of
loop without having written the current table name into curtable and
therefore calling strcmp() with uninitialized buffer. Avoid this by
setting curtable to zero upon declaration.

Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Florian Westphal <fw@strlen.de>