fix: fixing null pointer exception error (#1709)

Signed-off-by: Ayushman Gaur <ayushmangaur2017@gmail.com>

Author: Ayushman-Gaur

tools/flagd-core/src/main/java/dev/openfeature/contrib/tools/flagd/core/FlagdCore.java

@@ -270,11 +270,14 @@ private <T> ProviderEvaluation<T> resolve(Class<T> type, String key, T defaultVa
 
     private static ImmutableMetadata getFlagMetadata(Map<String, Object> currentFlagSetMetadata, FeatureFlag flag) {
         ImmutableMetadata.ImmutableMetadataBuilder metadataBuilder = ImmutableMetadata.builder();
-        for (Map.Entry<String, Object> entry : currentFlagSetMetadata.entrySet()) {
-            addEntryToMetadataBuilder(metadataBuilder, entry.getKey(), entry.getValue());
+
+        if (currentFlagSetMetadata != null) {
+            for (Map.Entry<String, Object> entry : currentFlagSetMetadata.entrySet()) {
+                addEntryToMetadataBuilder(metadataBuilder, entry.getKey(), entry.getValue());
+            }
         }
 
-        if (flag != null) {
+        if (flag != null && flag.getMetadata() != null) {
             for (Map.Entry<String, Object> entry : flag.getMetadata().entrySet()) {
                 addEntryToMetadataBuilder(metadataBuilder, entry.getKey(), entry.getValue());
             }

tools/flagd-core/src/test/java/dev/openfeature/contrib/tools/flagd/core/FlagdCoreTest.java

@@ -1,6 +1,7 @@
 package dev.openfeature.contrib.tools.flagd.core;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatNoException;
 
 import dev.openfeature.contrib.tools.flagd.api.FlagStoreException;
 import dev.openfeature.sdk.ImmutableContext;
@@ -127,4 +128,25 @@ void setFlagsAndGetChangedKeys_detectsRemovedFlags() throws FlagStoreException {
         // Then: boolFlag should be in the changed keys (it was removed)
         assertThat(changedKeys).contains("boolFlag");
     }
+
+    @Test
+    void resolveBooleanValue_flagWithNullMetadata_doesNotThrowNPE() {
+        String configWithNullMetadata = "{"
+                + "\"$schema\": \"https://flagd.dev/schema/v0/flags.json\","
+                + "\"flags\": {"
+                + "  \"nullMetadataFlag\": {"
+                + "    \"state\": \"ENABLED\","
+                + "    \"defaultVariant\": \"on\","
+                + "    \"variants\": { \"on\": true }"
+                + "  }"
+                + "}"
+                + "}";
+
+        assertThatNoException().isThrownBy(() -> {
+            flagdCore.setFlags(configWithNullMetadata);
+            ProviderEvaluation<Boolean> result =
+                    flagdCore.resolveBooleanValue("nullMetadataFlag", false, new ImmutableContext());
+            assertThat(result.getFlagMetadata()).isNotNull();
+        });
+    }
 }