Guard against null first record and null/blank fieldApiName

force-app/main/default/classes/CollectionGetFirstValue_Records.cls

@@ -14,6 +14,13 @@ public with sharing class CollectionGetFirstValue_Records {
             }
 
             SObject firstRecord = req.records[0];
+
+            if (firstRecord == null || String.isBlank(req.fieldApiName)) {
+                resp.response = null;
+                results.add(resp);
+                continue;
+            }
+
             Object fieldValue = firstRecord.get(req.fieldApiName);
 
             resp.response = (fieldValue == null) ? null : String.valueOf(fieldValue);

force-app/main/default/classes/CollectionGetFirstValue_RecordsTest.cls

@@ -49,4 +49,50 @@ public with sharing class CollectionGetFirstValue_RecordsTest {
         System.assertEquals(null, responses[0].response, 'Null records should result in null response');
     }
 
+    @IsTest
+    static void testGetFirstValue_NullFirstRecord() {
+        CollectionGetFirstValue_Records.Request req = new CollectionGetFirstValue_Records.Request();
+        req.records = new List<SObject>{ null };
+        req.fieldApiName = 'Name';
+
+        List<CollectionGetFirstValue_Records.Request> requests = new List<CollectionGetFirstValue_Records.Request>{ req };
+
+        List<CollectionGetFirstValue_Records.Response> responses = CollectionGetFirstValue_Records.getFirstValue(requests);
+
+        System.assertEquals(1, responses.size());
+        System.assertEquals(null, responses[0].response, 'Null first record should result in null response');
+    }
+
+    @IsTest
+    static void testGetFirstValue_NullFieldApiName() {
+        Account a = new Account(Name = 'Test Account');
+
+        CollectionGetFirstValue_Records.Request req = new CollectionGetFirstValue_Records.Request();
+        req.records = new List<SObject>{ a };
+        req.fieldApiName = null;
+
+        List<CollectionGetFirstValue_Records.Request> requests = new List<CollectionGetFirstValue_Records.Request>{ req };
+
+        List<CollectionGetFirstValue_Records.Response> responses = CollectionGetFirstValue_Records.getFirstValue(requests);
+
+        System.assertEquals(1, responses.size());
+        System.assertEquals(null, responses[0].response, 'Null fieldApiName should result in null response');
+    }
+
+    @IsTest
+    static void testGetFirstValue_BlankFieldApiName() {
+        Account a = new Account(Name = 'Test Account');
+
+        CollectionGetFirstValue_Records.Request req = new CollectionGetFirstValue_Records.Request();
+        req.records = new List<SObject>{ a };
+        req.fieldApiName = '   ';
+
+        List<CollectionGetFirstValue_Records.Request> requests = new List<CollectionGetFirstValue_Records.Request>{ req };
+
+        List<CollectionGetFirstValue_Records.Response> responses = CollectionGetFirstValue_Records.getFirstValue(requests);
+
+        System.assertEquals(1, responses.size());
+        System.assertEquals(null, responses[0].response, 'Blank fieldApiName should result in null response');
+    }
+
 }