Fix NullPointerException.

Signed-off-by: Adrián Boimvaser <adrianboimvaser@gmail.com>

Author: adrianboimvaser

src/main/java/org/openhab/binding/zwave/internal/ZWaveConfigProvider.java

@@ -290,14 +290,16 @@ public ConfigDescription getConfigDescription(URI uri, Locale locale) {
 
             for (int code = 1; code <= userCodeClass.getNumberOfSupportedCodes(); code++) {
                 UserCode userCode = userCodeClass.getCachedUserCode(code);
+                boolean readOnly =
+                        userCode != null && userCode.getState() == UserIdStatusType.RESERVED_BY_ADMINISTRATOR;
                 parameters.add(ConfigDescriptionParameterBuilder
                         .create(ZWaveBindingConstants.CONFIGURATION_USERCODE_LABEL + code, Type.TEXT)
                         .withLabel("Code " + code + " Label").withDescription("Name for user code " + code)
                         .withGroupName("usercode").build());
                 parameters.add(ConfigDescriptionParameterBuilder
                         .create(ZWaveBindingConstants.CONFIGURATION_USERCODE_CODE + code, Type.TEXT)
                         .withLabel("Code " + code).withDescription("Set the user code (4 to 10 numbers)")
-                        .withReadOnly(userCode.getState() == UserIdStatusType.RESERVED_BY_ADMINISTRATOR)
+                        .withReadOnly(readOnly)
                         .withGroupName("usercode").build());
             }
         }