Fixed main method usage when text is missing for encode or decode

lib/src/main/java/com/uwyn/urlencoder/UrlEncoder.java

@@ -237,9 +237,9 @@ public final class UrlEncoder {
             var option = args.remove(0);
             if (option.equals("-d")) {
                 perform_decode = true;
-                valid_arguments = true;
+                valid_arguments = !args.isEmpty();
             } else if (option.equals("-e")) {
-                valid_arguments = true;
+                valid_arguments = !args.isEmpty();
             } else {
                 args.clear();
             }

lib/src/test/java/com/uwyn/urlencoder/UrlEncoderTest.java

@@ -59,6 +59,20 @@ class UrlEncoderTest {
         assertTrue(result.output.contains("Usage :"));
     }
 
+    @Test
+    void testMainMissingEncodeText() {
+        var result = UrlEncoder.processMain(new String[] {"-e"});
+        assertEquals(1, result.status);
+        assertTrue(result.output.contains("Usage :"));
+    }
+
+    @Test
+    void testMainMissingDecodeText() {
+        var result = UrlEncoder.processMain(new String[] {"-d"});
+        assertEquals(1, result.status);
+        assertTrue(result.output.contains("Usage :"));
+    }
+
     @Test
     void testMainWrongArgs1() {
         var result = UrlEncoder.processMain(new String[] {"-p"});