Fix crash when saving peaks workspace.

If for some reason one of the radii is not defined SaveNexus crashes
because we access the value without checking it first. We should just
check that both radii are present, then write them out.

(cherry picked from commit 5e7dc01597680694128a3897d2244238f17e145a)

Framework/DataObjects/src/PeakShapeSpherical.cpp

@@ -53,13 +53,10 @@ std::string PeakShapeSpherical::toJSON() const {
   Json::Value root;
   PeakShapeBase::buildCommon(root);
   root["radius"] = Json::Value(m_radius);
-  // Check that there is an inner radius before writing
-  if (m_backgroundInnerRadius.is_initialized()) {
+
+  if (m_backgroundInnerRadius && m_backgroundOuterRadius) {
     root["background_outer_radius"] =
         Json::Value(m_backgroundOuterRadius.get());
-  }
-  // Check that there is an outer radius before writing
-  if (m_backgroundOuterRadius.is_initialized()) {
     root["background_inner_radius"] =
         Json::Value(m_backgroundInnerRadius.get());
   }