several one-line panic, race, and logic fixes (#7766)

api4/command.go

@@ -156,8 +156,8 @@ func listCommands(c *Context, w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	commands := []*model.Command{}
-	err := &model.AppError{}
+	var commands []*model.Command
+	var err *model.AppError
 	if customOnly {
 		if !c.App.SessionHasPermissionToTeam(c.Session, teamId, model.PERMISSION_MANAGE_SLASH_COMMANDS) {
 			c.SetPermissionError(model.PERMISSION_MANAGE_SLASH_COMMANDS)

api4/system.go

@@ -315,11 +315,11 @@ func addLicense(c *Context, w http.ResponseWriter, r *http.Request) {
 	fileData := fileArray[0]
 
 	file, err := fileData.Open()
-	defer file.Close()
 	if err != nil {
 		c.Err = model.NewAppError("addLicense", "api.license.add_license.open.app_error", nil, err.Error(), http.StatusBadRequest)
 		return
 	}
+	defer file.Close()
 
 	buf := bytes.NewBuffer(nil)
 	io.Copy(buf, file)

api4/team.go

@@ -623,10 +623,14 @@ func importTeam(c *Context, w http.ResponseWriter, r *http.Request) {
 	}
 
 	importFromArray, ok := r.MultipartForm.Value["importFrom"]
+	if !ok || len(importFromArray) < 1 {
+		c.Err = model.NewAppError("importTeam", "api.team.import_team.no_import_from.app_error", nil, "", http.StatusBadRequest)
+		return
+	}
 	importFrom := importFromArray[0]
 
 	fileSizeStr, ok := r.MultipartForm.Value["filesize"]
-	if !ok {
+	if !ok || len(fileSizeStr) < 1 {
 		c.Err = model.NewAppError("importTeam", "api.team.import_team.unavailable.app_error", nil, "", http.StatusBadRequest)
 		return
 	}
@@ -651,11 +655,11 @@ func importTeam(c *Context, w http.ResponseWriter, r *http.Request) {
 	fileInfo := fileInfoArray[0]
 
 	fileData, err := fileInfo.Open()
-	defer fileData.Close()
 	if err != nil {
 		c.Err = model.NewAppError("importTeam", "api.team.import_team.open.app_error", nil, err.Error(), http.StatusBadRequest)
 		return
 	}
+	defer fileData.Close()
 
 	var log *bytes.Buffer
 	switch importFrom {