Prevent null pointer

app/src/main/java/eu/faircode/email/ContactInfo.java

@@ -459,7 +459,10 @@ public class ContactInfo {
                             }
 
                         if (info.bitmap == null)
-                            throw ex;
+                            if (ex == null)
+                                throw new FileNotFoundException();
+                            else
+                                throw ex;
 
                         // Add to cache
                         File output = new File(dir,