Remove out of date code in DoStringPrintfV().

We can't clear a NULL buffer, the code didn't make any sense any more because
it wasn't updated when the function was changed as part of UTF-8 transition.

Closes #12529.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@65685 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/string.cpp

@@ -2012,11 +2012,6 @@ static int DoStringPrintfV(wxString& str,
         if ( !buf )
         {
             // out of memory
-
-            // in UTF-8 build, leaving uninitialized junk in the buffer
-            // could result in invalid non-empty UTF-8 string, so just
-            // reset the string to empty on failure:
-            buf[0] = '\0';
             return -1;
         }