verify, validate: fix the blank-stdin sentinel check, getJsonsOrBlank yields '{}' not '', so the argument forms never worked.

validate.go

@@ -51,7 +51,8 @@ nak event -k 1 -p not_a_pubkey | nak validate
 		}
 
 		for stdinEvent := range getJsonsOrBlank() {
-			if stdinEvent == "" {
+			if stdinEvent == "{}" && !isPiped() {
+				// blank sentinel from getJsonsOrBlank(), use the arguments instead
 				for _, arg := range c.Args().Slice() {
 					if err := handleEvent(arg); err != nil {
 						ctx = lineProcessingError(ctx, "%s", err)

verify.go

@@ -19,7 +19,8 @@ it outputs nothing if the verification is successful.`,
 	Action: func(ctx context.Context, c *cli.Command) error {
 		for stdinEvent := range getJsonsOrBlank() {
 			evt := nostr.Event{}
-			if stdinEvent == "" {
+			if stdinEvent == "{}" && !isPiped() {
+				// blank sentinel from getJsonsOrBlank(), use the argument instead
 				stdinEvent = c.Args().First()
 				if stdinEvent == "" {
 					continue