decouple Offspec from GISAS: the former has always a spherical detector

GUI/Model/Device/InstrumentItems.cpp

@@ -756,8 +756,8 @@ const ICoordSystem* OffspecInstrumentItem::createCoordSystem() const
         new FixedBinAxis("alpha", m_alphaAxis.nbins(), m_alphaAxis.min() * Units::deg,
                          m_alphaAxis.max() * Units::deg);
 
-    const auto* det = dynamic_cast<const SphericalDetector*>(
-        detectorItem()->createDetector().get());
+    const auto* det =
+        dynamic_cast<const SphericalDetector*>(detectorItem()->createDetector().get());
     ASSERT(det);
     return det->offspecCoords(alphaAxis);
 }