Merge pull request #7083 from mheon/6983_bugfix

Fix Panic with -t and -a stderr
Upstream-commit: 5948b105e7dcc7428e9525ccb44d543169b47a6e
Component: engine

components/engine/api/client/hijack.go

@@ -88,7 +88,7 @@ func (cli *DockerCli) hijack(method, path string, setRawTerminal bool, in io.Rea
 			}()
 
 			// When TTY is ON, use regular copy
-			if setRawTerminal {
+			if setRawTerminal && stdout != nil {
 				_, err = io.Copy(stdout, br)
 			} else {
 				_, err = utils.StdCopy(stdout, stderr, br)