add null check for pipe_ptr

Author: haoxian2

src/acl_kernel.cpp

@@ -436,6 +436,9 @@ CL_API_ENTRY cl_int CL_API_CALL clSetKernelArgIntelFPGA(cl_kernel kernel,
   // shouldn't spend time setting up the argument properly.
   if (is_pipe) {
     cl_mem pipe_ptr = *((cl_mem *)arg_value);
+    if (pipe_ptr == 0) {
+      ERR_RET(CL_INVALID_ARG_VALUE, context, "Pipe value is NULL");
+    }
 
     kernel->arg_is_svm[arg_index] = CL_FALSE;
     kernel->arg_is_ptr[arg_index] = CL_FALSE;