Fix failure when compiling on OS X with Sip version 4.12.

sipClass_QVariant was undefined so it appears it is still
required to be defined at Sip 4.12. This has not been tested on
other platforms with this Sip version so may not be a final fix.

git-svn-id: http://svn.osgeo.org/qgis/trunk@15205 c8812cc2-4d05-0410-92ff-de0c093fc19c

python/core/conversions.sip

@@ -37,7 +37,7 @@ template <TYPE>
 #if (SIP_VERSION >= 0x040900)
 #define sipClass_QString ((sipWrapperType *) sipTypeAsPyTypeObject (sipType_QString))
 #endif
-#if (SIP_VERSION >= 0x040900 && SIP_VERSION < 0x040c00)
+#if (SIP_VERSION >= 0x040900 && SIP_VERSION <= 0x040c00)
 #define sipClass_QVariant ((sipWrapperType *) sipTypeAsPyTypeObject (sipType_QVariant))
 #endif
 %End