Resolve comments related to Evaluator

Author: Varun Rathore

src/main/java/com/google/firebase/remoteconfig/ConditionEvaluator.java

@@ -20,6 +20,7 @@
 import static com.google.common.base.Preconditions.checkNotNull;
 
 import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableMap;
 import com.google.firebase.internal.NonNull;
 import com.google.firebase.internal.Nullable;
 
@@ -57,12 +58,15 @@ Map<String, Boolean> evaluateConditions(
       @Nullable KeysAndValues context) {
     checkNotNull(conditions, "List of conditions must not be null.");
     checkArgument(!conditions.isEmpty(), "List of conditions must not be empty.");
+    if(context == null || conditions.isEmpty()){
+      return ImmutableMap.of();
+    }
     KeysAndValues evaluationContext = context != null 
         ? context 
         : new KeysAndValues.Builder().build();
 
     Map<String, Boolean> evaluatedConditions = conditions.stream()
-        .collect(Collectors.toMap(
+        .collect(ImmutableMap.toImmutableMap(
             ServerCondition::getName,
             condition -> 
                 evaluateCondition(condition.getCondition(), evaluationContext, /* nestingLevel= */0)

src/main/java/com/google/firebase/remoteconfig/ServerTemplateImpl.java

@@ -93,11 +93,8 @@ public ServerConfig evaluate(@Nullable KeysAndValues context)
     }
 
     ConditionEvaluator conditionEvaluator = new ConditionEvaluator();
-    ImmutableMap<String, Boolean> evaluatedCondition = 
-        context != null && !cache.getServerConditions().isEmpty()
-        ? ImmutableMap.copyOf(
-          conditionEvaluator.evaluateConditions(cache.getServerConditions(), context))
-        : ImmutableMap.of();
+    ImmutableMap<String, Boolean> evaluatedCondition = ImmutableMap.copyOf(
+      conditionEvaluator.evaluateConditions(cache.getServerConditions(), context));
     ImmutableMap<String, Parameter> parameters = ImmutableMap.copyOf(cache.getParameters());
     mergeDerivedConfigValues(evaluatedCondition, parameters, configValues);