app: at: Delete char not added to AT command

Delete (0x7F) used to delete previous character
but delete byte 0x7F was added to AT command buffer
resulting in syntax error.
Delete is not added to the AT command anymore.

Jira: SM-330

Signed-off-by: Tommi Rantanen <tommi.rantanen@nordicsemi.no>

Author: trantanen

app/src/sm_at_host.c

@@ -1272,7 +1272,7 @@ static size_t cmd_rx_handler(struct sm_at_host_ctx *ctx, uint8_t c)
 		} else {
 			ctx->prev_character = '\0';
 		}
-		break;
+		goto handle_echo;
 	default:
 		break;
 	}