Check null before passing to Integer.parseInt

Just after user data is cleared, user preference associated with
PREF_KEYBOARD_LAYOUT is always empty. In such case, we might
want to return the default value immediately, rather than
calling Integer.parseInt(null) and catching NumberFormatException
unnecessarily.

BUG: 13472379
Change-Id: I8dca9a22780d057013c032bd1f56e730dcada3ce

java/src/com/android/inputmethod/latin/settings/Settings.java

@@ -273,6 +273,9 @@ public final class Settings implements SharedPreferences.OnSharedPreferenceChang
     public static int readKeyboardThemeIndex(final SharedPreferences prefs, final Resources res) {
         final int defaultThemeIndex = readDefaultKeyboardThemeIndex(res);
         final String themeIndexString = prefs.getString(PREF_KEYBOARD_LAYOUT, null);
+        if (themeIndexString == null) {
+            return defaultThemeIndex;
+        }
         try {
             return Integer.parseInt(themeIndexString);
         } catch (final NumberFormatException e) {