Don't crash on startup if NFC is not available

src/org/fdroid/fdroid/FDroid.java

@@ -423,6 +423,7 @@ public class FDroid extends FragmentActivity {
     private void setupAndroidBeam() {
         PackageManager pm = getPackageManager();
         NfcAdapter nfcAdapter = NfcAdapter.getDefaultAdapter(this);
+        if (nfcAdapter != null) {
             ApplicationInfo appInfo;
             try {
                 appInfo = pm.getApplicationInfo("org.fdroid.fdroid",
@@ -437,3 +438,4 @@ public class FDroid extends FragmentActivity {
             }
         }
     }
+}