Fixed ffmpeg not found cause sys panic bug

.gitignore

@@ -38,3 +38,5 @@ src/system/smtp_conf.json
 src/mod/**/system/auth/authlog.db
 src/mod/**/system/auth/authlog.db.lock
 src/launcher.exe
+.DS_Store
+src/ffmpeg

src/mod/agi/agi.ffmpeg.go

@@ -29,12 +29,12 @@ func (g *Gateway) FFmpegLibRegister() {
 	_, err := exec.LookPath("ffmpeg")
 	if err != nil {
 		logger.PrintAndLog("Agi", "ffmpeg not found in PATH", nil)
-		os.Exit(1)
+		return
 	}
 	err = g.RegisterLib("ffmpeg", g.injectFFmpegFunctions)
 	if err != nil {
 		logger.PrintAndLog("Agi", fmt.Sprint(err), nil)
-		os.Exit(1)
+		return
 	}
 }