strip slashes from instance domain to avoid crash

app/src/main/java/com/keylesspalace/tusky/LoginActivity.kt

@@ -320,6 +320,10 @@ class LoginActivity : AppCompatActivity() {
             // Strip any schemes out.
             var s = domain.replaceFirst("http://", "")
             s = s.replaceFirst("https://", "")
+
+            //strip out any slashes that might have been added
+            s = s.replace("/", "")
+
             // If a username was included (e.g. username@example.com), just take what's after the '@'.
             val at = s.lastIndexOf('@')
             if (at != -1) {