fix: Do not throw exception when path to cached jvm installations does not exist.

HMCLCore/src/main/java/org/jackhuang/hmcl/download/java/JavaRepository.java

@@ -43,12 +43,15 @@ public final class JavaRepository {
         Optional<String> platformOptional = getCurrentJavaPlatform();
         if (platformOptional.isPresent()) {
             String platform = platformOptional.get();
-            for (Path component : Files.newDirectoryStream(getJavaStoragePath())) {
-                Path javaHome = component.resolve(platform).resolve(component.getFileName());
-                try {
-                    addJava(javaHome);
-                } catch (IOException e) {
-                    LOG.log(Level.WARNING, "Failed to determine Java at " + javaHome, e);
+            Path javaStoragePath = getJavaStoragePath();
+            if (Files.isDirectory(javaStoragePath)) {
+                for (Path component : Files.newDirectoryStream(javaStoragePath)) {
+                    Path javaHome = component.resolve(platform).resolve(component.getFileName());
+                    try {
+                        addJava(javaHome);
+                    } catch (IOException e) {
+                        LOG.log(Level.WARNING, "Failed to determine Java at " + javaHome, e);
+                    }
                 }
             }
         }