llm: Check for nil memory data before printing

We dump out our best memory estimate after we complete processing
for any reason, including errors. This is helpful for finding what
what stopped us in error conditions but in some cases we might not
have gotten even the first result yet.

Fixes #11957

llm/server.go

@@ -651,7 +651,9 @@ func (s *ollamaServer) Load(ctx context.Context, gpus discover.GpuInfoList, requ
 		if !success {
 			s.initModel(ctx, LoadRequest{}, LoadOperationClose)
 		}
+		if s.mem != nil {
 			s.mem.Log(slog.LevelInfo)
+		}
 	}()
 
 	slog.Info("loading model", "model layers", s.totalLayers, "requested", s.options.NumGPU)