drm/amd/display: Add otg_master NULL check within resource_log_pipe_topology_update

[Why]
Coverity reports NULL_RETURN warning.

[How]
Add otg_master NULL check.
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Acked-by: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Hersen Wu <hersenxs.wu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/core/dc_resource.c

@@ -2329,6 +2329,9 @@ void resource_log_pipe_topology_update(struct dc *dc, struct dc_state *state)
 					state->stream_status[stream_idx].mall_stream_config.paired_stream);
 			otg_master = resource_get_otg_master_for_stream(
 					&state->res_ctx, state->streams[phantom_stream_idx]);
+			if (!otg_master)
+				continue;
+
 			resource_log_pipe_for_stream(dc, state, otg_master, stream_idx);
 		}
 	}