add null check for pipe_ptr

Author: haoxian2

src/acl_kernel.cpp

@@ -442,7 +442,7 @@ CL_API_ENTRY cl_int CL_API_CALL clSetKernelArgIntelFPGA(cl_kernel kernel,
     kernel->arg_defined[arg_index] = 1;
 
     /* If this is a host pipe, create a host channel and bind them together */
-    if (arg_info->host_accessible && pipe_ptr->host_pipe_info != NULL) {
+    if (arg_info->host_accessible && pipe_ptr && pipe_ptr->host_pipe_info != NULL) {
       if (pipe_ptr->host_pipe_info->m_binded_kernel != NULL) {
         ERR_RET(CL_INVALID_ARG_VALUE, context,
                 "This pipe has already been bound to a kernel. Cannot "