Only set slot to OCCUPIED on successful key loading

Signed-off-by: Ryan Everett <ryan.everett@arm.com>
diff --git a/library/psa_crypto_slot_management.c b/library/psa_crypto_slot_management.c
index 36d5410..38e3273 100644
--- a/library/psa_crypto_slot_management.c
+++ b/library/psa_crypto_slot_management.c
@@ -221,7 +221,6 @@
     if (status != PSA_SUCCESS) {
         goto exit;
     }
-    slot->status = PSA_SLOT_OCCUPIED;
 
 #if defined(MBEDTLS_PSA_CRYPTO_SE_C)
     /* Special handling is required for loading keys associated with a
@@ -243,6 +242,11 @@
 #endif /* MBEDTLS_PSA_CRYPTO_SE_C */
 
     status = psa_copy_key_material_into_slot(slot, key_data, key_data_length);
+    if (status != PSA_SUCCESS){
+        goto exit;
+    }
+
+    slot->status = PSA_SLOT_OCCUPIED;
 
 exit:
     psa_free_persistent_key_data(key_data, key_data_length);