Run check completion before error checking

Running check completion before error checking allows for completion of flags when no character has been typed yet

app.go

@@ -126,6 +126,10 @@ func (a *App) Run(arguments []string) (err error) {
 	}
 	context := NewContext(a, set, nil)
 
+	if checkCompletions(context) {
+		return nil
+	}
+
 	if err != nil {
 		fmt.Fprintln(a.Writer, "Incorrect Usage.")
 		fmt.Fprintln(a.Writer)
@@ -133,10 +137,6 @@ func (a *App) Run(arguments []string) (err error) {
 		return err
 	}
 
-	if checkCompletions(context) {
-		return nil
-	}
-
 	if !a.HideHelp && checkHelp(context) {
 		ShowAppHelp(context)
 		return nil
@@ -233,6 +233,10 @@ func (a *App) RunAsSubcommand(ctx *Context) (err error) {
 		return nerr
 	}
 
+	if checkCompletions(context) {
+		return nil
+	}
+
 	if err != nil {
 		fmt.Fprintln(a.Writer, "Incorrect Usage.")
 		fmt.Fprintln(a.Writer)
@@ -240,10 +244,6 @@ func (a *App) RunAsSubcommand(ctx *Context) (err error) {
 		return err
 	}
 
-	if checkCompletions(context) {
-		return nil
-	}
-
 	if len(a.Commands) > 0 {
 		if checkSubcommandHelp(context) {
 			return nil