Fix Giphy crash

src/org/thoughtcrime/securesms/giph/model/ChunkedImageUrl.java

@@ -14,7 +14,7 @@ public class ChunkedImageUrl implements Key {
   public static final long SIZE_UNKNOWN = -1;
 
   private final String url;
-  private final long   size;
+  private final long size;
 
   public ChunkedImageUrl(@NonNull String url) {
     this(url, SIZE_UNKNOWN);
@@ -22,7 +22,7 @@ public class ChunkedImageUrl implements Key {
 
   public ChunkedImageUrl(@NonNull String url, long size) {
     this.url = url;
-    this.size   = size;
+    this.size = size;
   }
 
   public String getUrl() {
@@ -35,6 +35,7 @@ public class ChunkedImageUrl implements Key {
 
   @Override
   public void updateDiskCacheKey(@NonNull MessageDigest messageDigest) {
+    if (url == null) { return; }
     messageDigest.update(url.getBytes());
     messageDigest.update(Conversions.longToByteArray(size));
   }
@@ -45,12 +46,14 @@ public class ChunkedImageUrl implements Key {
 
     ChunkedImageUrl that = (ChunkedImageUrl)other;
 
+    if (this.url == null || that.url == null) { return false; }
+
     return this.url.equals(that.url) && this.size == that.size;
   }
 
   @Override
   public int hashCode() {
+    if (url == null) { return 0; }
     return url.hashCode() ^ (int)size;
   }
-
 }