ant -Debug would cause a NullPointerException

PR: 22065


git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@275022 13f79535-47bb-0310-9956-ffa450edef68

src/main/org/apache/tools/ant/Main.java

@@ -378,6 +378,9 @@ public class Main implements AntMain {
                     name = name.substring(0, posEq);
                 } else if (i < args.length - 1) {
                     value = args[++i];
+                } else {
+                    throw new BuildException("Missing value for property "
+                                             + name);
                 }
 
                 definedProps.put(name, value);