Add placeholder image asset

android/gradle.properties

 org.gradle.jvmargs=-Xmx1536M
 android.useAndroidX=true
 android.enableJetifier=true
-app.versionName=0.0.10
-app.versionCode=10
+app.versionName=0.0.11
+app.versionCode=11

lib/screens/game_pick_word.dart

@@ -51,13 +51,16 @@ class GamePickWordPage extends StatelessWidget {
   }
 
   Container _buildImageContainer(String image, Color color) {
+    String imageAsset = 'assets/placeholder.png';
+    if (image != null) {
+        imageAsset = 'assets/images/'+image;
+    }
+
     return Container(
       padding: EdgeInsets.all(10),
       child: FlatButton(
         color: Colors.teal,
-        child: image == null ?
-          Text('') :
-          Image(image: AssetImage('assets/images/'+image)),
+        child: Image(image: AssetImage(imageAsset)),
       ),
     );
   }

pubspec.yaml

@@ -22,3 +22,4 @@ flutter:
     - assets/assets_images.json
     - assets/files/
     - assets/images/
+    - assets/placeholder.png