fix compilation in !wxUSE_LOG_DIALOG case (closes #10411)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@58265 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/generic/logg.cpp

@@ -340,6 +340,7 @@ wxLogGui::DoShowMultipleLogMessages(const wxArrayString& messages,
 #else // !wxUSE_LOG_DIALOG
     // start from the most recent message
     wxString message;
+    const size_t nMsgCount = messages.size();
     str.reserve(nMsgCount*100);
     for ( size_t n = nMsgCount; n > 0; n-- ) {
         message << m_aMessages[n - 1] << wxT("\n");