corrected warnings when compiling with -Wall -W

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@15353 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/generic/paletteg.cpp

@@ -72,6 +72,7 @@ wxPalette::wxPalette(int n, const unsigned char *red, const unsigned char *green
 }
 
 wxPalette::wxPalette(const wxPalette& palette)
+    : wxGDIObject()
 {
     Ref(palette);
 }