check if image decoding succeeded before using the result

Fixes #6061
Closes #6080
// FREEBIE

src/org/thoughtcrime/securesms/util/BitmapUtil.java

@@ -59,6 +59,10 @@ public class BitmapUtil {
                                                       constraints.getImageMaxHeight(context),
                                                       DecodeFormat.PREFER_RGB_565);
 
+    if (scaledBitmap == null) {
+      throw new BitmapDecodingException("Unable to decode image");
+    }
+    
     try {
       do {
         ByteArrayOutputStream baos = new ByteArrayOutputStream();