fix: use QPixmapCache only from the main thread

It's a required condition.

Signed-off-by: flow <flowlnlnln@gmail.com>

launcher/Application.cpp

@@ -90,6 +90,7 @@
 #include <QIcon>
 
 #include "InstanceList.h"
+#include "MTPixmapCache.h"
 
 #include <minecraft/auth/AccountList.h>
 #include "icons/IconList.h"
@@ -134,6 +135,8 @@
 
 static const QLatin1String liveCheckFile("live.check");
 
+PixmapCache* PixmapCache::s_instance = nullptr;
+
 namespace {
 void appDebugOutput(QtMsgType type, const QMessageLogContext &context, const QString &msg)
 {
@@ -693,6 +696,9 @@ Application::Application(int &argc, char **argv) : QApplication(argc, argv)
             m_globalSettingsProvider->addPage<AccountListPage>();
             m_globalSettingsProvider->addPage<APIPage>();
         }
+
+        PixmapCache::setInstance(new PixmapCache(this));
+
         qDebug() << "<> Settings loaded.";
     }