Fix wxHTML parse bug in non-unicode, ? characters are not displayed.

GetEntitiesParser()->GetCharForCode(NBSP_UNICODE_VALUE) in the non-unicode
build returns the value '?' as it doesn't find a match for that value.  The
parser then proceeds to replace all '?' characters in the HTML document with
NBSP.

Change the type of the #define to be unsigned int rather than wxChar for
non-unicode to fix this.

Closes #17692.

src/html/winpars.cpp

@@ -338,10 +338,11 @@ wxFSFile *wxHtmlWinParser::OpenURL(wxHtmlURLType type,
     return GetFS()->OpenFile(myurl, flags);
 }
 
-#define NBSP_UNICODE_VALUE  (wxChar(160))
 #if !wxUSE_UNICODE
+    #define NBSP_UNICODE_VALUE  (160U)
     #define CUR_NBSP_VALUE m_nbsp
 #else
+    #define NBSP_UNICODE_VALUE  (wxChar(160))
     #define CUR_NBSP_VALUE NBSP_UNICODE_VALUE
 #endif