obmc-console: fix segfault on missing config

The `obmc-console-client` allow to not specify configuration file for
active session. But at the same time it does not tolerate null pointer
passed as config. This leads to a segmentation fault due to a missing
configuration file.

Fix this small inconvenience.

Added testcase to make sure that obmc-console-client doesn't segfault
when invoked without any arguments.

Output without the fix:
'''
+ /home/dev/obmc-console/build/obmc-console-client
+ grep Connection refused
Segmentation fault (core dumped)
'''

Output with the fix:
'''
+ /home/ninad/dev/1110_ghe/obmc-console/build/obmc-console-client
+ grep Connection refused
+ cleanup
+ cd -
+ rm -rf /tmp/test_console_client_no_args_3245394.DZqk0S
'''

Change-Id: Ia83da8bca30e2be94e00066f20f2cbe2ccba23b6
Tested-by: Ninad Palsule <ninad@linux.ibm.com>
Signed-off-by: Ninad Palsule <ninad@linux.ibm.com>
Signed-off-by: Igor Kononenko <i.kononenko.e@gmail.com>

config.c

diff --git a/config.c b/config.c
index f36af8c..855ef38 100644
--- a/config.c
+++ b/config.c
@@ -43,7 +43,7 @@
 	char buf[CONFIG_MAX_KEY_LENGTH];
 	int rc;
 
-	if (!config->dict) {
+	if (!config || !config->dict) {
 		return NULL;
 	}
 

test/meson.build

diff --git a/test/meson.build b/test/meson.build
index d36d15c..61411b8 100644
--- a/test/meson.build
+++ b/test/meson.build
@@ -55,6 +55,7 @@
 client_tests = [
   'test-console-client-can-read',
   'test-console-client-can-write',
+  'test-console-client-no-args',
 ]
 
 foreach ct : client_tests

test/test-console-client-no-args

diff --git a/test/test-console-client-no-args b/test/test-console-client-no-args
new file mode 100755
index 0000000..f90b5c0
--- /dev/null
+++ b/test/test-console-client-no-args
@@ -0,0 +1,21 @@
+#!/usr/bin/sh
+
+set -eux
+
+CLIENT="$3"
+
+# Meet DBus bus and path name constraints, append own PID for parallel runs
+TEST_NAME="$(basename "$0" | tr '-' '_')"_${$}
+TEST_DIR="$(mktemp --tmpdir --directory "${TEST_NAME}.XXXXXX")"
+
+cd "$TEST_DIR"
+
+cleanup()
+{
+  cd -
+  rm -rf "$TEST_DIR"
+}
+
+trap cleanup EXIT
+
+$CLIENT 2>&1 >/dev/null | grep 'Connection refused'