Duplicate set before using putStringSet()

As per the documentation:

> Note that you must not modify the set instance returned by this call. The consistency of the stored data is not guaranteed if you do, nor is your ability to modify the instance at all.

Fix #1129

app/src/main/java/fr/neamar/kiss/DataHandler.java

@@ -403,13 +403,17 @@ public Set<String> getExcluded() {
     }
 
     public void addToExcludedFromHistory(AppPojo app) {
-        Set<String> excluded = getExcludedFromHistory();
+        // The set needs to be cloned and then edited,
+        // modifying in place is not supported by putStringSet()
+        Set<String> excluded = new HashSet<>(getExcludedFromHistory());
         excluded.add(app.id);
         PreferenceManager.getDefaultSharedPreferences(context).edit().putStringSet("excluded-apps-from-history", excluded).apply();
     }
 
     public void addToExcluded(AppPojo app) {
-        Set<String> excluded = getExcluded();
+        // The set needs to be cloned and then edited,
+        // modifying in place is not supported by putStringSet()
+        Set<String> excluded = new HashSet<>(getExcluded());
         excluded.add(app.getComponentName());
         PreferenceManager.getDefaultSharedPreferences(context).edit().putStringSet("excluded-apps", excluded).apply();
     }

app/src/main/java/fr/neamar/kiss/SettingsActivity.java

@@ -169,7 +169,9 @@ private void addExcludedAppSettings(final SharedPreferences prefs) {
             @Override
             @SuppressWarnings("unchecked")
             public boolean onPreferenceChange(Preference preference, Object newValue) {
-                Set<String> appListToBeExcluded = (HashSet<String>) newValue;
+                // Duplicate then save to make sure we're not editing in place
+                // (can't be done with sharedpreferences)
+                Set<String> appListToBeExcluded = new HashSet<>((HashSet<String>) newValue);
 
                 prefs.edit().putStringSet("excluded-apps", appListToBeExcluded).apply();
                 loadExcludedAppsToPreference(multiPreference);