Only detects ANSI color codes for data in string type

Signed-off-by: Cocoa <0xbbc@0xbbc.com>

lib/appenders/file.js

@@ -56,7 +56,10 @@ function fileAppender(file, layout, logSize, numBackups, options, timezoneOffset
     if (options.removeColor === true) {
       // eslint-disable-next-line no-control-regex
       const regex = /\x1b[[0-9;]*m/g;
-      loggingEvent.data = loggingEvent.data.map(d => d.replace(regex, ''))
+      loggingEvent.data = loggingEvent.data.map(d => {
+        if (typeof d === 'string') return d.replace(regex, '')
+        else return d
+      })
     }
     if (!writer.write(layout(loggingEvent, timezoneOffset) + eol, "utf8")) {
       process.emit('log4js:pause', true);