[webnfc] Handle the case of android.nfc.tech.Ndef.getNdefMessage() returning null

android.nfc.tech.Ndef.getNdefMessage() may return null when the tag is
formatted but is empty, we need to handle the case well.
See
https://developer.android.com/reference/android/nfc/tech/Ndef.html#getNdefMessage().

BUG=520391

Change-Id: I49cdf40978ad837546dcb050ce8e7d2cac4662ce
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1736167
Auto-Submit: Leon Han <leon.han@intel.com>
Reviewed-by: Reilly Grant <reillyg@chromium.org>
Commit-Queue: Leon Han <leon.han@intel.com>
Cr-Commit-Position: refs/heads/master@{#684220}

services/device/nfc/android/java/src/org/chromium/device/nfc/NfcImpl.java

@@ -557,17 +557,20 @@ public class NfcImpl implements Nfc {
         try {
             mTagHandler.connect();
             message = mTagHandler.read();
+            if (message == null) {
+                Log.w(TAG, "Cannot read data from NFC tag. Tag is empty.");
+                return;
+            }
             if (message.getByteArrayLength() > NdefMessage.MAX_SIZE) {
                 Log.w(TAG, "Cannot read data from NFC tag. NdefMessage exceeds allowed size.");
                 return;
             }
+            notifyMatchingWatchers(message, mTagHandler.compatibility());
         } catch (TagLostException e) {
             Log.w(TAG, "Cannot read data from NFC tag. Tag is lost.");
         } catch (FormatException | IllegalStateException | IOException e) {
             Log.w(TAG, "Cannot read data from NFC tag. IO_ERROR.");
         }
-
-        if (message != null) notifyMatchingWatchers(message, mTagHandler.compatibility());
     }
 
     /**