test: Search for non-existent message should return nothing

test: Search for non-existent message should return nothing

My scripts expect that empty search result is actually empty. Since
commit 6dcb7592, even empty search prints a newline character and this
breaks my scripts.

This patch adds a test for this bug. In the test I cannot use
test_expect_equal function as $() operator suppresses the final
newline and this kind of difference is not detected.

 test/search |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)