AdditionalLauncher.java: Fix AdditionalLauncher.PropertyFile to handle property expressions without "=".

Author: alexeysemenyukoracle

test/jdk/tools/jpackage/helpers/jdk/jpackage/test/AdditionalLauncher.java

@@ -393,7 +393,13 @@ public static final class PropertyFile {
         PropertyFile(Path path) throws IOException {
             data = Files.readAllLines(path).stream().map(str -> {
                 return str.split("=", 2);
-            }).collect(toMap(tokens -> tokens[0], tokens -> tokens[1], (oldValue, newValue) -> {
+            }).collect(toMap(tokens -> tokens[0], tokens -> {
+                if (tokens.length == 1) {
+                    return "";
+                } else {
+                    return tokens[1];
+                }
+            }, (oldValue, newValue) -> {
                 return newValue;
             }));
         }