CMake: Make sure null-configuration items do not end up in output

Make sure there are no empty strings returned by null configuration
items visible in the output.

Change-Id: I467f33f41b8eeb25b6cb2b1aa3ada4dd7e1d5950
Reviewed-by: Vikas Pachdha <vikas.pachdha@theqtcompany.com>
Reviewed-by: Tim Jenssen <tim.jenssen@theqtcompany.com>

src/plugins/cmakeprojectmanager/cmakekitinformation.cpp

@@ -308,6 +308,7 @@ QStringList CMakeConfigurationKitInformation::toStringList(const Kit *k)
     QStringList current
             = Utils::transform(CMakeConfigurationKitInformation::configuration(k),
                                [](const CMakeConfigItem &i) { return i.toString(); });
+    current = Utils::filtered(current, [](const QString &s) { return !s.isEmpty(); });
     Utils::sort(current);
     return current;
 }