ipc4: fixed possible null dereference

Result of the function call ipc_get_comp_by_id() had been dereferenced
without checking whether the pointer may be null.
Returned pointer may be null when component does not exist on the
list.

Signed-off-by: Andrey Borisovich <andrey.borisovich@intel.com>

src/ipc/ipc4/helper.c

@@ -632,6 +632,8 @@ int ipc4_pipeline_complete(struct ipc *ipc, uint32_t comp_id)
 	int ret;
 
 	ipc_pipe = ipc_get_pipeline_by_id(ipc, comp_id);
+	if (!ipc_pipe)
+		return -IPC4_INVALID_RESOURCE_ID;
 
 	/* Pass IPC to target core */
 	if (!cpu_is_me(ipc_pipe->core))