Avoid setting null compiler option

See gh-36971

Author: omaryaya

spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/main/java/org/springframework/boot/maven/AbstractAotMojo.java

@@ -53,6 +53,7 @@
  *
  * @author Phillip Webb
  * @author Scott Frederick
+ * @author Omar YAYA
  * @since 3.0.0
  */
 public abstract class AbstractAotMojo extends AbstractDependencyFilterMojo {
@@ -152,10 +153,7 @@ protected final void compileSourceFiles(URL[] classPath, File sourcesDirectory,
 				options.add(releaseVersion);
 			}
 			else {
-				options.add("--source");
-				options.add(compilerConfiguration.getSourceMajorVersion());
-				options.add("--target");
-				options.add(compilerConfiguration.getTargetMajorVersion());
+				setSourceAndTargetVersions(compilerConfiguration, options);
 			}
 			options.addAll(new RunArguments(this.compilerArguments).getArgs());
 			Iterable<? extends JavaFileObject> compilationUnits = fileManager.getJavaFileObjectsFromPaths(sourceFiles);
@@ -167,6 +165,19 @@ protected final void compileSourceFiles(URL[] classPath, File sourcesDirectory,
 			}
 		}
 	}
+	private static void setSourceAndTargetVersions(JavaCompilerPluginConfiguration compilerConfiguration,
+			List<String> options) {
+		String sourceMajorVersion = compilerConfiguration.getSourceMajorVersion();
+		if (sourceMajorVersion != null && !sourceMajorVersion.isEmpty()) {
+			options.add("--source");
+			options.add(sourceMajorVersion);
+		}
+		String targetMajorVersion = compilerConfiguration.getTargetMajorVersion();
+		if (targetMajorVersion != null && !targetMajorVersion.isEmpty()) {
+			options.add("--target");
+			options.add(targetMajorVersion);
+		}
+	}
 
 	protected final URL[] getClassPath(File[] directories, ArtifactsFilter... artifactFilters)
 			throws MojoExecutionException {