corrected a bug in ConcatSelf() induced by the latest change

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@743 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/string.cpp

@@ -441,9 +441,8 @@ void wxString::ConcatSelf(int nSrcLen, const char *pszSrcData)
 {
   STATISTICS_ADD(SummandLength, nSrcLen);
 
-  // concatenating an empty string is a NOP, but it happens quite rarely,
-  // so we don't waste our time checking for it
-  // if ( nSrcLen > 0 )
+  // concatenating an empty string is a NOP
+  if ( nSrcLen > 0 ) {
     wxStringData *pData = GetStringData();
     size_t nLen = pData->nDataLength;
     size_t nNewLen = nLen + nSrcLen;
@@ -479,6 +478,8 @@ void wxString::ConcatSelf(int nSrcLen, const char *pszSrcData)
     m_pchData[nNewLen] = '\0';              // put terminating '\0'
     GetStringData()->nDataLength = nNewLen; // and fix the length
   }
+  //else: the string to append was empty
+}
 
 /*
  * concatenation functions come in 5 flavours: