ATLAS-1415: fix potential NPE issues found by Coverity scan

webapp/src/main/java/org/apache/atlas/web/adapters/AtlasStructFormatConverter.java

@@ -125,7 +125,13 @@ public class AtlasStructFormatConverter extends AtlasAbstractFormatConverter {
             ret = new HashMap<>();
 
             for (AtlasStructDef.AtlasAttributeDef attrDef : getAttributeDefs(structType)) {
-                AtlasType            attrType      = structType.getAttributeType(attrDef.getName());
+                AtlasType attrType = structType.getAttributeType(attrDef.getName());
+
+                if (attrType == null) {
+                    LOG.warn("ignored attribute {}.{}: failed to find AtlasType", structType.getTypeName(), attrDef.getName());
+                    continue;
+                }
+
                 AtlasFormatConverter attrConverter = converterRegistry.getConverter(attrType.getTypeCategory());
 
                 Object v2Value = attributes.get(attrDef.getName());

webapp/src/main/java/org/apache/atlas/web/rest/EntitiesREST.java

@@ -174,9 +174,13 @@ public class EntitiesREST {
         AtlasEntity.AtlasEntities atlasEntities = entitiesStore.searchEntities(searchFilter);
         AtlasEntityHeader.AtlasEntityHeaders entityHeaders = new AtlasEntityHeader.AtlasEntityHeaders();
         entityHeaders.setList(new LinkedList<AtlasEntityHeader>());
-        for (AtlasEntity atlasEntity : atlasEntities.getList()) {
-            entityHeaders.getList().add(new AtlasEntityHeader(atlasEntity.getTypeName(), atlasEntity.getAttributes()));
+
+        if (atlasEntities != null) {
+            for (AtlasEntity atlasEntity : atlasEntities.getList()) {
+                entityHeaders.getList().add(new AtlasEntityHeader(atlasEntity.getTypeName(), atlasEntity.getAttributes()));
+            }
         }
+
         return entityHeaders;
     }