Fix NPE in CommandLine.resolveOption(String).

Author: garydgregory

src/changes/changes.xml

@@ -49,6 +49,9 @@
       <action dev="ggregory" type="fix" due-to="Alexander Veit, Gary Gregory" issue="CLI-318">
         Inconsistent date format in changes report.
       </action>
+      <action dev="ggregory" type="fix" due-to="Dilraj Singh, Gary Gregory" issue="CLI-283">
+        Fix NPE in CommandLine.resolveOption(String).
+      </action>
       <!-- ADD -->
       <action type="update" dev="ggregory" due-to="Dependabot, Gary Gregory">
         Add github/codeql-action.

src/main/java/org/apache/commons/cli/CommandLine.java

@@ -439,16 +439,17 @@ public Iterator<Option> iterator() {
     /**
      * Retrieves the option object given the long or short option as a String
      *
-     * @param opt short or long name of the option.
+     * @param opt short or long name of the option, may be null.
      * @return Canonicalized option.
      */
-    private Option resolveOption(String opt) {
-        opt = Util.stripLeadingHyphens(opt);
-        for (final Option option : options) {
-            if (opt.equals(option.getOpt()) || opt.equals(option.getLongOpt())) {
-                return option;
+    private Option resolveOption(final String opt) {
+        final String actual = Util.stripLeadingHyphens(opt);
+        if (actual != null) {
+            for (final Option option : options) {
+                if (actual.equals(option.getOpt()) || actual.equals(option.getLongOpt())) {
+                    return option;
+                }
             }
-
         }
         return null;
     }

src/test/java/org/apache/commons/cli/bug/BugsTest.java

@@ -20,6 +20,7 @@
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
 
@@ -135,6 +136,9 @@ public void test11680() throws Exception {
 
         cmd.getOptionValue("f", "default f");
         cmd.getOptionValue("m", "default m");
+        //
+        assertNull(cmd.getOptionValue((String) null, null));
+        assertEquals("default", cmd.getOptionValue((String) null, "default"));
     }
 
     @Test