IVGCVSW-3670 Fix Vts Tests after adding Ref Import functionality

Signed-off-by: Ferran Balaguer <ferran.balaguer@arm.com>
Change-Id: I87d003ae14575d7d7be67b2a7d00d69ef6201849
diff --git a/src/backends/reference/RefTensorHandle.cpp b/src/backends/reference/RefTensorHandle.cpp
index 59ccec6..42ac7f0 100644
--- a/src/backends/reference/RefTensorHandle.cpp
+++ b/src/backends/reference/RefTensorHandle.cpp
@@ -35,7 +35,10 @@
     if (!m_Pool)
     {
         // unmanaged
-        ::operator delete(m_UnmanagedMemory);
+        if (!m_Imported)
+        {
+            ::operator delete(m_UnmanagedMemory);
+        }
     }
 }
 
@@ -110,6 +113,12 @@
             // Checks the 16 byte memory alignment.
             if (reinterpret_cast<uint64_t>(memory) % 16)
             {
+                if (m_Imported)
+                {
+                    m_Imported = false;
+                    m_UnmanagedMemory = nullptr;
+                }
+
                 return false;
             }