[dbus] init ActiveScanResult to zero (#1814)

Avoid crashes when the compiler does not automatically initialize the
scan results to zero.

This behavior was not expressing itself on x86_64 platforms, but did
cause crashes on an ARM Cortex-A7.
diff --git a/src/dbus/server/dbus_thread_object.cpp b/src/dbus/server/dbus_thread_object.cpp
index 782db3c..b76bb4b 100644
--- a/src/dbus/server/dbus_thread_object.cpp
+++ b/src/dbus/server/dbus_thread_object.cpp
@@ -382,7 +382,7 @@
     {
         for (const auto &r : aResult)
         {
-            ActiveScanResult result;
+            ActiveScanResult result = {};
 
             result.mExtAddress = ConvertOpenThreadUint64(r.mExtAddress.m8);
             result.mPanId      = r.mPanId;