After Maven packages the Swing project, it cannot be started. It can be started in IDEA.

the Swing project created by Idea uses maven to solve dependency problems
it can be successful if it is run directly in idea, but it is not successful after packaging.
related pom is as follows

<plugin>
        <artifactId>maven-assembly-plugin</artifactId>
        <version>2.6</version>
        <configuration>
          <!-- archivearchivejar -->
          <archive>
            <manifest>
              <mainClass>com.chinatsp.App</mainClass>
            </manifest>
          </archive>
          <!-- jar-with-dependencies -->
          <!-- descriptor -->
          <descriptorRefs>
            <descriptorRef>jar-with-dependencies</descriptorRef>
          </descriptorRefs>
        </configuration>
        <executions>
          <execution>
            <id>make-assembly</id>
            <!-- phasegoalsmavenmaven -->
            <!-- installprojectpackage phasesingle goal -->
            <phase>package</phase>
            <goals>
              <goal>single</goal>
            </goals>
          </execution>
        </executions>
      </plugin>

After

is packaged, run the program and display

 java -jar tools-1.0-jar-with-dependencies.jar
Exception in thread "main" java.lang.NullPointerException
        at com.chinatsp.App.<init>(App.java:23)
        at com.chinatsp.App.main(App.java:69)

is there a big boss to help solve it?