[PATCH 2/3] shared/shell: fix -std=c23 build failure

[Rudi Heitbaum <rudi@xxxxxxxxxxxx>]

gcc-15 switched to -std=c23 by default:

    https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=55e3bd376b2214e200fa76d12b67ff259b06c212

As a result `bluez` fails the build as:

    src/shared/shell.c:365:24: error: incompatible types when returning type '_Bool' but 'struct input *' was expected
      365 |                 return false;
          |                        ^~~~~

Signed-off-by: Rudi Heitbaum <rudi@xxxxxxxxxxxx>
---
 src/shared/shell.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/shared/shell.c b/src/shared/shell.c
index a8fa87696..aa6c16c8c 100644
--- a/src/shared/shell.c
+++ b/src/shared/shell.c
@@ -362,7 +362,7 @@ static struct input *input_new(int fd)
 
 	io = io_new(fd);
 	if (!io)
-		return false;
+		return NULL;
 
 	input = new0(struct input, 1);
 	input->io = io;
-- 
2.43.0