Fix crash caused by transfer account spinner

Sometimes the view received in onItemSelected is null, causing a
NullPointerException.

I couldn't reproduce the crash, although the fix seems evident.

Fixes http://crashes.to/s/93f65e0f4e6

Author: rivaldi8

app/src/main/java/org/gnucash/android/ui/transaction/TransactionFormFragment.java

@@ -322,9 +322,11 @@ public void onActivityCreated(Bundle savedInstanceState) {
 
             @Override
             public void onItemSelected(AdapterView<?> adapterView, View view, int position, long id) {
-                // Remove the favorite star from the view to avoid visual clutter.
-                TextView qualifiedAccountName = (TextView) view;
-                qualifiedAccountName.setCompoundDrawablesWithIntrinsicBounds(0,0,0,0);
+                if (view != null) {
+                    // Remove the favorite star from the view to avoid visual clutter.
+                    TextView qualifiedAccountName = (TextView) view;
+                    qualifiedAccountName.setCompoundDrawablesWithIntrinsicBounds(0, 0, 0, 0);
+                }
 
                 if (mSplitsList.size() == 2) { //when handling simple transfer to one account
                     for (Split split : mSplitsList) {