[vulkan] Drop lights with size 0

They can't contribute any light, so no point in keeping them. Fixes the
erroneous size-0 shadow maps in the second nq demo.

libs/video/renderer/vulkan/vulkan_lighting.c

@@ -969,9 +969,12 @@ Vulkan_LoadLights (model_t *model, const char *entity_data, vulkan_ctx_t *ctx)
 				qfv_light_t light = {};
 
 				parse_light (&light, entity, targets);
+				// some lights have 0 output, so drop them
+				if (light.light) {
 					DARRAY_APPEND (&lctx->lights, light);
 				}
 			}
+		}
 		for (size_t i = 0; i < ctx->frames.size; i++) {
 			lightingframe_t *lframe = &lctx->frames.a[i];
 			DARRAY_RESIZE (&lframe->lightvis, lctx->lights.size);