git diff bug? what problem may be here

When after editing I get this:
 mdi.Application= this;

 mdi.Class.TApplication.baseConstructor.apply( this, arguments );

git diff shows:
 
  mdi.Application= this;
- mdi.Class.TApplication.baseConstructor.apply( this, arguments );
 
- //We must not create/show application node because of this is the 'document.bo
- //It exists always so apply application properties to 'document.body' only
- this.updateDomNode();
+ mdi.Class.TApplication.baseConstructor.apply( this, arguments );
 },{

Notice same lines:
- mdi.Class.TApplication.baseConstructor.apply( this, arguments );
+ mdi.Class.TApplication.baseConstructor.apply( this, arguments );

But when I edit like this (notice no new line between mdi.Application and mdi.Class):

 mdi.Application= this;
 mdi.Class.TApplication.baseConstructor.apply( this, arguments );

Git diff shows:
  mdi.Application= this;
  mdi.Class.TApplication.baseConstructor.apply( this, arguments );
-
- //We must not create/show application node because of this is the 'document.body'.
- //It exists always so apply application properties to 'document.body' only
- this.updateDomNode();
 },{

Why new line cause same line in patch added and removed?