shill: cellular: Avoid shill crash when there's no SIM card inserted.

BUG=chromium-os:33409
TEST=unit tests, tested on device

Change-Id: If1b0c1ab50107150d97eab659d577eba21a0ba8f
Reviewed-on: https://gerrit.chromium.org/gerrit/30401
Tested-by: Darin Petkov <petkov@chromium.org>
Reviewed-by: Gary Morain <gmorain@chromium.org>
Commit-Ready: Darin Petkov <petkov@chromium.org>
diff --git a/dbus_properties_proxy.cc b/dbus_properties_proxy.cc
index dfb6d17..d24f734 100644
--- a/dbus_properties_proxy.cc
+++ b/dbus_properties_proxy.cc
@@ -23,10 +23,10 @@
   try {
     return proxy_.GetAll(interface_name);
   } catch (const DBus::Error &e) {
-    LOG(FATAL) << "DBus exception: " << e.name() << ": " << e.what()
+    LOG(ERROR) << "DBus exception: " << e.name() << ": " << e.what()
                << " interface name: " << interface_name;
-    return DBusPropertiesMap();  // Make the compiler happy.
   }
+  return DBusPropertiesMap();
 }
 
 void DBusPropertiesProxy::set_properties_changed_callback(