Json type variable parsing issue fixes (#40)

Author: Tan108

src/main/kotlin/com/featurevisor/sdk/Instance+Evaluation.kt

@@ -475,7 +475,7 @@ fun FeaturevisorInstance.evaluateVariable(
 
         // initial
         if (!statuses.ready && initialFeatures?.get(featureKey)?.variables?.get(variableKey) != null) {
-            val variableValue = initialFeatures?.get(featureKey)?.variables?.get(variableKey)
+            val variableValue = initialFeatures[featureKey]?.variables?.get(variableKey)
             evaluation = Evaluation(
                 featureKey = featureKey,
                 reason = INITIAL,

src/main/kotlin/com/featurevisor/sdk/Instance+Variable.kt

@@ -84,7 +84,7 @@ inline fun <reified T : Any> FeaturevisorInstance.getVariableObject(
     }
 }
 
-inline fun <reified T : Any> FeaturevisorInstance.getVariableJSON(
+inline fun <reified T> FeaturevisorInstance.getVariableJSON(
     featureKey: FeatureKey,
     variableKey: VariableKey,
     context: Context,