Initialize GError* to NULL before calling g_dbus_proxy_new_syn

This fixes the crash issue of power_control when manually build and
replace executable or library.
The reason why it does not crash on a full OpenBMC build may be due to
the prelink clear the stack (not sure).

Fixes openbmc/openbmc#818.

Change-Id: I17b0e2188ebe14815d67a7f07eba4906bde75e3c
Signed-off-by: Lei YU <mine260309@gmail.com>
diff --git a/libopenbmc_intf/power_gpio.c b/libopenbmc_intf/power_gpio.c
index 3c44c81..1e7d9cd 100644
--- a/libopenbmc_intf/power_gpio.c
+++ b/libopenbmc_intf/power_gpio.c
@@ -25,7 +25,7 @@
 gboolean read_power_gpio(GDBusConnection *connection, PowerGpio *power_gpio)
 {
 	GDBusProxy *proxy;
-	GError *error;
+	GError *error = NULL;
 	GVariant *value;
 	gchar *power_good_in_name;
 	gchar *latch_out_name;