Fixes null pointer exception when run without main command (#276)

core/app.go

@@ -144,7 +144,6 @@ func (a *App) Run() {
 	if err != nil {
 		log.Errorf("Unable to parse command arguments: %v", err)
 	}
-	cmd.Name = "APP"
 	a.Command = cmd
 
 	a.handleSignals()
@@ -160,6 +159,7 @@ func (a *App) Run() {
 	a.handlePolling()
 
 	if a.Command != nil {
+		cmd.Name = "APP"
 		// Run our main application and capture its stdout/stderr.
 		// This will block until the main application exits and then os.Exit
 		// with the exit code of that application.

integration_tests/tests/test_no_command/docker-compose.yml

@@ -0,0 +1,6 @@
+app:
+    image: "cpfix_app"
+    mem_limit: 128m
+    volumes:
+      - '${CONTAINERPILOT_BIN}:/bin/containerpilot:ro'
+    command: /bin/containerpilot

integration_tests/tests/test_no_command/run.sh

@@ -0,0 +1,14 @@
+#!/bin/bash
+
+logFail() {
+    echo "${1}"
+    exit 1
+}
+
+docker-compose run -d app
+TEST_ID=$(docker ps -a | awk -F' +' '/testnocommand/{print $1}')
+docker logs $TEST_ID | grep -qv panic
+result=$?
+docker stop $TEST_ID || logFail 'should still be running'
+docker rm $TEST_ID
+exit $result