_param_str_split is used to split ?foo=1;bar=2 into a dictionary, but throws
an exception if a lone semicolon is used as the value doesn't split into two
items.
Fix by checking that the result of the first split has content.
(Bitbake rev: 7662f8c8676d87cb318f811423cc02fe8cb146f6)
Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>