Added missing @NotNull annotations

Author: MartelliEnrico

buildSrc/src/main/java/com/github/stickerifier/stickerify/JlinkJavaLauncher.java

@@ -7,7 +7,7 @@
 import org.gradle.jvm.toolchain.JavaLauncher;
 import org.jetbrains.annotations.NotNull;
 
-public record JlinkJavaLauncher(Provider<JavaInstallationMetadata> metadata, Provider<RegularFile> executablePath) implements JavaLauncher {
+public record JlinkJavaLauncher(Provider<@NotNull JavaInstallationMetadata> metadata, Provider<@NotNull RegularFile> executablePath) implements JavaLauncher {
 	public JlinkJavaLauncher(JlinkTask task) {
 		this(task.getJavaCompiler().map(JavaCompiler::getMetadata), task.getOutputDirectory().file("jre/bin/java"));
 	}

buildSrc/src/main/java/com/github/stickerifier/stickerify/JlinkTask.java

@@ -92,10 +92,10 @@ public void createJre() {
 		}
 
 		if (result.getExitValue() != 0) {
-			if (!stderrStr.isEmpty()) {
-				getLogger().log(LogLevel.ERROR, stderrStr);
-			} else {
+			if (stderrStr.isEmpty()) {
 				getLogger().log(LogLevel.ERROR, "jlink failed with exit code: {}", result.getExitValue());
+			} else {
+				getLogger().log(LogLevel.ERROR, stderrStr);
 			}
 		}