Fix bug that prevented selecting insecure SMS

Fixes #6929

// FREEBIE

src/org/thoughtcrime/securesms/ConversationActivity.java

@@ -240,6 +240,7 @@ public class ConversationActivity extends PassphraseRequiredActionBarActivity
   private boolean    isSecureText;
   private boolean    isDefaultSms          = true;
   private boolean    isMmsEnabled          = true;
+  private boolean    isSecurityInitialized = false;
 
   private final IdentityRecordList identityRecords = new IdentityRecordList();
   private final DynamicTheme       dynamicTheme    = new DynamicTheme();
@@ -918,8 +919,13 @@ public class ConversationActivity extends PassphraseRequiredActionBarActivity
   }
 
   private void handleSecurityChange(boolean isSecureText, boolean isDefaultSms) {
+    if (isSecurityInitialized && isSecureText == this.isSecureText && isDefaultSms == this.isDefaultSms) {
+      return;
+    }
+
     this.isSecureText          = isSecureText;
     this.isDefaultSms          = isDefaultSms;
+    this.isSecurityInitialized = true;
 
     boolean isMediaMessage = recipient.isMmsGroupRecipient() || attachmentManager.isAttachmentPresent();