fix hadling of DesignStrength

src/E2Sextupole.cpp

@@ -747,11 +747,12 @@ void E2Sextupole::write_DesignStrength(Tango::WAttribute &attr)
 	//	Add your own code
 	/* clang-format off */
 	*attr_DesignStrength_read = w_val;
-	if (design_strength_initialized == false){
+	if (design_strength_initialized == false){ // only with a value of DesignStrength init process can be completed
 		design_strength_initialized = true;
 		init_strengths();
 		subscribe_events();
 	}
+	else init_strengths();
 	/*----- PROTECTED REGION END -----*/	//	E2Sextupole::write_DesignStrength
 }