Don't open a room by default on mobile

Since the room window is fullscreen on mobile and you can't see the room list,
the first thing you'll be doing is backing out so you can choose the actual room you want to see

src/roommanager.cpp

@@ -14,6 +14,7 @@
 #include "urlhelper.h"
 
 #include <KLocalizedString>
+#include <KRuntimePlatform>
 #include <QDesktopServices>
 #include <QQuickTextDocument>
 #include <QStandardPaths>
@@ -241,6 +242,12 @@ void RoomManager::loadInitialRoom()
         resolveResource(m_arg);
     }
 
+    const auto runtimePlatform = KRuntimePlatform::runtimePlatform();
+    if (runtimePlatform.contains(QStringLiteral("phone")) || runtimePlatform.contains(QStringLiteral("handset"))) {
+        // We don't want to open a room on startup on mobile
+        return;
+    }
+
     if (m_currentRoom) {
         // we opened a room with the arg parsing already
         return;