Fix compilation issue (typo) in BsFlags.h

Source/BansheeUtility/Include/BsFlags.h

@@ -162,7 +162,7 @@ namespace BansheeEngine
 
 		Flags<Enum, Storage>& operator^= (const Flags<Enum, Storage>& rhs)
 		{
-			mBits ^= f.mBits;
+			mBits ^= rhs.mBits;
 
 			return *this;
 		}
@@ -232,4 +232,4 @@ namespace BansheeEngine
 		inline Flags<Enum, Storage> operator~(Enum a) { return ~Flags<Enum, Storage>(a); }
 
 	 /** @} */
-}
+}