Parse share-targets defined by non-main activities

Some system apps do not have any launcher icons but want to publish
sharing shortcuts. As a fix, all activities are parsed for their XML
resource, which implies some of these shortcut may not hold an
activity. This CL removes that assumption from launcher side.

Bug: 136353429
Test: Manual test
Change-Id: I2994da17fe078b2fab61a614c1326fddd5fd8571
diff --git a/src/com/android/launcher3/model/BgDataModel.java b/src/com/android/launcher3/model/BgDataModel.java
index 32fce0b..fdfcef1 100644
--- a/src/com/android/launcher3/model/BgDataModel.java
+++ b/src/com/android/launcher3/model/BgDataModel.java
@@ -424,7 +424,8 @@
         // Now add the new shortcuts to the map.
         for (ShortcutInfo shortcut : shortcuts) {
             boolean shouldShowInContainer = shortcut.isEnabled()
-                    && (shortcut.isDeclaredInManifest() || shortcut.isDynamic());
+                    && (shortcut.isDeclaredInManifest() || shortcut.isDynamic())
+                    && shortcut.getActivity() != null;
             if (shouldShowInContainer) {
                 ComponentKey targetComponent
                         = new ComponentKey(shortcut.getActivity(), shortcut.getUserHandle());