Polish "Avoid setting null compiler option"

See gh-36971

Author: snicoll

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

@@ -153,7 +153,16 @@ protected final void compileSourceFiles(URL[] classPath, File sourcesDirectory,
 				options.add(releaseVersion);
 			}
 			else {
-				setSourceAndTargetVersions(compilerConfiguration, options);
+				String source = compilerConfiguration.getSourceMajorVersion();
+				if (source != null) {
+					options.add("--source");
+					options.add(source);
+				}
+				String target = compilerConfiguration.getTargetMajorVersion();
+				if (target != null) {
+					options.add("--target");
+					options.add(target);
+				}
 			}
 			options.addAll(new RunArguments(this.compilerArguments).getArgs());
 			Iterable<? extends JavaFileObject> compilationUnits = fileManager.getJavaFileObjectsFromPaths(sourceFiles);
@@ -165,19 +174,6 @@ 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 {