[IE9] Bgcolor partial removal problematic

[Garry Yao]

1. Load the editor with the following content and selection:

   <p>
   	This is <span style="background-color: rgb(255, 0, 0);">some [sample] text</span>. </p>
   
   

2. Open background color panel and apply the 'auto' color to selection;

• Actual Result:

  <p>
  	This is <span style="">some </span>sample<span style=""> text</span>.</p>
  

• Expected Result:

  <p>
  	This is <span style="background-color: rgb(255, 0, 0);">some </span>sample<span style="background-color: rgb(255, 0, 0);"> text</span>.</p>
  

[Garry Yao]

Not a recent regression, dedicate to IE9 only.

[Jakub Ś]

Confirmed. Reproducible on IE9 only.