Don't divide by zero.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_4_BRANCH@20921 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

contrib/src/fl/rowlayoutpl.cpp

@@ -456,6 +456,9 @@ void cbRowLayoutPlugin::ApplyLengthRatios( cbRowInfo* pRow )
         }
     }  // for
 
+    if (pcntSum == 0.0)
+        pcntSum = 1.0;
+
     if ( haveSquished )
         unit = freeSpc / pcntSum;