Compile fix

Amends 198b1f5fa5.

Change-Id: I9174b96269bb05a79bbc491afd8f70a1896e0e24
Reviewed-by: André Hartmann <aha_1980@gmx.de>

src/plugins/coreplugin/messagemanager.cpp

@@ -29,6 +29,8 @@
 
 #include <extensionsystem/pluginmanager.h>
 
+#include <utils/qtcassert.h>
+
 using namespace Core;
 
 static MessageManager *m_instance = nullptr;