Do not call setAlwaysButtonEnabled if the activity doesn't support defaults.

13405c552956eee529462eb8004ca3eab4273a8b introduced a bug where
activities using ResolverActivity without dafaults/always option get selected,
the ResolverActivity tries to set a default causing a crash.

Test: Test Application using TECH_DISCOVERED intent filter
Bug: 38358120
Change-Id: Id36635d84963bcf1dc7e55938e2370542ed291ab
diff --git a/core/java/com/android/internal/app/ResolverActivity.java b/core/java/com/android/internal/app/ResolverActivity.java
index 80f4b99..ceb06f5 100644
--- a/core/java/com/android/internal/app/ResolverActivity.java
+++ b/core/java/com/android/internal/app/ResolverActivity.java
@@ -1941,7 +1941,8 @@
             final int checkedPos = mAdapterView.getCheckedItemPosition();
             final boolean hasValidSelection = checkedPos != ListView.INVALID_POSITION;
             if (!useLayoutWithDefault()
-                    && (!hasValidSelection || mLastSelected != checkedPos)) {
+                    && (!hasValidSelection || mLastSelected != checkedPos)
+                    && mAlwaysButton != null) {
                 setAlwaysButtonEnabled(hasValidSelection, checkedPos, true);
                 mOnceButton.setEnabled(hasValidSelection);
                 if (hasValidSelection) {