Why does squid returns header error with ssl_bump configuration?

Issue

• Why does squid returns header error with ssl_bump configuration? Disabling ssl-bump does not show the error.
  For example, the particular site returns following header error with ssl-bump feature.

  26 2015/02/03 12:56:03 kid1| ctx: enter level  0: 'https://example.com/crossdomain.xml'
       27 2015/02/03 12:56:03 kid1| WARNING: HTTP header contains NULL characters {Date: Tue, 03 Feb 2015 03:57:20 GMT
       28 X-Content-Type-Options: nosniff
       29 X-XSS-Protection: 1; mode=block
       30 X-Frame-Options: SAMEORIGIN
       31 Access-Control-Allow-Origin: *
       32 Last-Modified: Wed, 04 Jun 2014 01:04:28 GMT
       33 Accept-Ranges: bytes
       34 Vary: Accept-Encoding
       35 Content-Encoding: gzip
       36 Content-Length: 252
       37 Content-Type: application/xml
       38 Age: 0
       39 Connection: keep-alive
       40 Strict-Transport-Security: max-age=15552000; includeSubDomains}
       41 NULL <--- NULL is HERE
       42 {Date: Tue, 03 Feb 2015 03:57:20 GMT
       43 X-Content-Type-Options: nosniff
       44 X-XSS-Protection: 1; mode=block
       45 X-Frame-Options: SAMEORIGIN
       46 Access-Control-Allow-Origin: *
       47 Last-Modified: Wed, 04 Jun 2014 01:04:28 GMT
       48 Accept-Ranges: bytes
       49 Vary: Accept-Encoding
       50 Content-Encoding: gzip
       51 Content-Length: 252
       52 Content-Type: application/xml
       53 Age: 0
       54 Connection: keep-alive
       55 Strict-Transport-Security: max-age=15552000; includeSubDomains
       56 2015/02/03 12:56:03 kid1| ctx: exit level  0
       57 2015/02/03 12:56:03 kid1| WARNING: HTTP: Invalid Response: Bad header encountered from https://example.com/crossdomain.xml AKA example.com/crossdomain.xml