fix "Create new key" layout in SelectSignKeyIdListFragment

OpenKeychain/src/main/res/layout/select_dummy_key_item.xml

@@ -2,6 +2,8 @@
 <TextView xmlns:android="http://schemas.android.com/apk/res/android"
     android:id="@+id/api_select_sign_key_create_key"
     android:background="?android:selectableItemBackground"
+    android:paddingTop="6dp"
+    android:paddingBottom="6dp"
     android:paddingLeft="8dp"
     android:paddingRight="8dp"
     android:textAppearance="?android:attr/textAppearanceMedium"
@@ -11,4 +13,5 @@
     android:drawableLeft="@drawable/ic_key_plus_grey600_24dp"
     android:drawablePadding="8dp"
     android:gravity="center_vertical"
-    android:clickable="true" />
+    android:minHeight="?listPreferredItemHeight"
+    />