Fix logic error in SplitterProxy::setEnabled

It clears the splitter when enabling it, that seems wrong.
Despite this bug, it still mostly worked before because the eventFilter checked
for _enabled anyway.

(cherry picked from commit 4b10546c)

kstyle/breezesplitterproxy.cpp

@@ -136,7 +136,7 @@ namespace Breeze
         if( _enabled != value )
         {
             _enabled = value;
-            if( _enabled ) clearSplitter();
+            if( !_enabled ) clearSplitter();
         }
     }