Correct UTF-32BE BOM detection in wxConvAuto.

On the fly detection of the BOM was wrongly implemented for UTF-32BE in
r63064 and returned BOM_None for it if we tried to read exactly 2 bytes.

Fix this by returning BOM_Unknown if the first 2 bytes are NUL.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@63246 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/convauto.cpp

@@ -107,11 +107,13 @@ wxConvAuto::BOMType wxConvAuto::DetectBOM(const char *src, size_t srcLen)
 
             if ( src[0] == '\x00' && src[1] == '\x00' )
             {
-                // this could only be UTF-32BE
+                // this could only be UTF-32BE, check that the data we have so
-                if ( srcLen == 3 && src[2] == '\xFE' )
+                // far allows for it
-                    return BOM_Unknown;
+                if ( srcLen == 3 && src[2] != '\xFE' )
-            }
+                    return BOM_None;
 
+                return BOM_Unknown;
+            }
             break;
 
         default: