Ensure initialized before synchronized block (#33)

* Ensure initialized before synchronized block

* Update actions

Author: alanocallaghan

.github/workflows/gradle.yml

@@ -30,11 +30,9 @@ jobs:
         java-version: '21'
         distribution: 'temurin'
     - name: Validate Gradle wrapper
-      uses: gradle/wrapper-validation-action@v1
+      uses: gradle/actions/wrapper-validation@v3
     - name: Build with Gradle
-      uses: gradle/gradle-build-action@v2
-      with:
-        arguments: build
+      run: ./gradlew build
     - uses: actions/upload-artifact@v4
       with:
         name: jar

src/main/java/qupath/ext/djl/DjlDnnModel.java

@@ -125,6 +125,7 @@ private void ensureInitialized() {
 
 	@Override
 	public Map<String, Mat> predict(Map<String, Mat> blobs) {
+		ensureInitialized();
 		synchronized (predictor) {
 			try {
 				var result = predictor.predict(blobs.values().stream().toArray(Mat[]::new));