smb2: destroy the context in case or errors from smb2_generic_cb

Errors can also be reported via generic cbs, that will cause the
vlc_smb2_mainloop to abort. In that case, we should destroy the smb2
context to fix the issue mentioned by 924c951518

(cherry picked from commit 960ef3f8ef)
Signed-off-by: Thomas Guillem <thomas@gllm.fr>

modules/access/smb2.c

@@ -257,6 +257,16 @@ vlc_smb2_mainloop(struct vlc_smb2_op *op)
         }
     }
 
+    if (op->error_status != 0 && op->smb2 != NULL)
+    {
+        /* An error was signalled from a smb2 cb. Destroy the smb2 context now
+         * since this call might still trigger callbacks using the current op
+         * (that is allocated on the stack). */
+        smb2_destroy_context(op->smb2);
+        op->smb2 = NULL;
+        *op->smb2p = NULL;
+    }
+
     return op->error_status;
 }