Added: Add empty and null strings tests for invalid urls to FileReceiverActivityTest

app/src/test/java/com/termux/filepicker/TermuxFileReceiverActivityTest.java

@@ -24,6 +24,8 @@ public class TermuxFileReceiverActivityTest {
 
         List<String> invalidUrls = new ArrayList<>();
         invalidUrls.add("a test with example.com");
+        invalidUrls.add("");
+        invalidUrls.add(null);
         for (String url : invalidUrls) {
             Assert.assertFalse(TermuxFileReceiverActivity.isSharedTextAnUrl(url));
         }