fix: added null or empty checks for basic auth credentials (#98)

Author: asadali214

src/main/java/io/apimatic/core/utilities/CoreHelper.java

@@ -1071,6 +1071,12 @@ public static String tryUrlEncode(String value, boolean spaceAsPercentEncoded) {
      */
     public static String getBase64EncodedCredentials(String basicAuthUserName,
             String basicAuthPassword) {
+        if (basicAuthUserName == null || basicAuthUserName.equals("")) {
+            return null;
+        }
+        if (basicAuthPassword == null || basicAuthPassword.equals("")) {
+            return null;
+        }
         String authCredentials = basicAuthUserName + ":" + basicAuthPassword;
         return "Basic " + Base64.getEncoder().encodeToString(authCredentials.getBytes());
     }

src/test/java/apimatic/core/utilities/CoreHelperTest.java

@@ -137,6 +137,26 @@ public void testBase64Encoding() {
         assertEquals(actualEncodedString, expectedEncodedString);
     }
 
+    @Test
+    public void testBase64EncodingWithNullValues() {
+        String actualEncodedString = CoreHelper.getBase64EncodedCredentials(null, "password");
+        assertEquals(null, actualEncodedString);
+        actualEncodedString = CoreHelper.getBase64EncodedCredentials("username", null);
+        assertEquals(null, actualEncodedString);
+        actualEncodedString = CoreHelper.getBase64EncodedCredentials(null, null);
+        assertEquals(null, actualEncodedString);
+    }
+
+    @Test
+    public void testBase64EncodingWithEmptyValues() {
+        String actualEncodedString = CoreHelper.getBase64EncodedCredentials("", "password");
+        assertEquals(null, actualEncodedString);
+        actualEncodedString = CoreHelper.getBase64EncodedCredentials("username", "");
+        assertEquals(null, actualEncodedString);
+        actualEncodedString = CoreHelper.getBase64EncodedCredentials("", "");
+        assertEquals(null, actualEncodedString);
+    }
+
     @Test
     public void testUrlEncoding() {
         String urlString = "https://localhost:8080%query=0";