Fix FGenericData to initialise its data on default construction

Src/Kernels/Generic/FGenericData.hpp

@@ -9,8 +9,8 @@ public:
     using multipole_t = Multipole;
     using local_expansion_t = LocalExpansion;
 private:
-    multipole_t m_data;
-    local_expansion_t l_data;
+    multipole_t m_data {};
+    local_expansion_t l_data {};
 public:
     multipole_t* up         = &m_data;
     local_expansion_t* down = &l_data;
@@ -22,7 +22,6 @@ public:
         return up != nullptr;
     }
 
-
     multipole_t& getMultipoleData() noexcept {
         return *up;
     }
@@ -37,6 +36,10 @@ public:
         return *down;
     }
 
+    /* TODO: Add getSavedSize if multipole and local_exp have it */
+
+    /* TODO: Add save/restore if multipole and local_exp have it */
+
 
     ///////////////////////////////////////////////////////
     // to extend FAbstractSendable