fixes npe issue with --stats

[munishchouhan]

This PR will fix the issue of getting NPE when using --stats for failed or cancelled pipelines

error:

tw % ./tw runs view -i 35vHNSjgrDPftA -w "community/showcase" --stats           
java.lang.NullPointerException
        at io.seqera.tower.cli.commands.runs.ViewCmd.exec(ViewCmd.java:147)
        at io.seqera.tower.cli.commands.AbstractApiCmd.call(AbstractApiCmd.java:436)
        at io.seqera.tower.cli.commands.AbstractApiCmd.call(AbstractApiCmd.java:67)
        at picocli.CommandLine.executeUserObject(CommandLine.java:1953)
        at picocli.CommandLine.access$1300(CommandLine.java:145)
        at picocli.CommandLine$RunLast.executeUserObjectOfLastSubcommandWithSameParent(CommandLine.java:2358)
        at picocli.CommandLine$RunLast.handle(CommandLine.java:2352)
        at picocli.CommandLine$RunLast.handle(CommandLine.java:2314)
        at picocli.CommandLine$AbstractParseResultHandler.execute(CommandLine.java:2179)
        at picocli.CommandLine$RunLast.execute(CommandLine.java:2316)
        at picocli.CommandLine.execute(CommandLine.java:2078)
        at io.seqera.tower.cli.Tower.main(Tower.java:101)
        at [email protected]/java.lang.invoke.LambdaForm$DMH/sa346b79c.invokeStaticInit(LambdaForm$DMH)

[munishchouhan]

tested after the fix:

tower-cli % ./tw runs view -i 35vHNSjgrDPftA -w "community/showcase" --stats
Running in Zsh
Note: Some input files use or override a deprecated API.
Note: Recompile with -Xlint:deprecation for details.
Note: Some input files use unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.

  Run at [community / showcase] workspace:


    General
    ---------------------+---------------------------------------------
     ID                  | 35vHNSjgrDPftA                              
     Operation ID        | cee67d72-90b4-4eae-b87c-5b51e33c3f9d        
     Run name            | hungry_church                               
     Status              | CANCELLED                                   
     Starting date       | No date reported                            
     Commit ID           | No commit ID reported                       
     Session ID          | e096d322-9386-4b9a-9adf-bfdf9cb8f54c        
     Username            | marvin-umali                                
     Workdir             | s3://nf-tower-bucket/scratch/35vHNSjgrDPftA 
     Container           | No container was reported                   
     Executors           | No executors were reported                  
     Compute Environment | AWS_Batch_Ireland_FusionV2_NVMe             
     Nextflow Version    | No Nextflow version reported                
     Labels              | owner=seqera,rnaseq,workspace=showcase      

    Stats
    ----------------+------------
     Wall Time      | nu minutes 
     CPU Time       | 0.00 hours 
     Total Memory   | 0.00 GB    
     Read           | 0.00 GB    
     Write          | 0.00 GB    
     Estimated Cost | $nu        

[munishchouhan]

@jordeu and @JaimeSeqLabs its a very small change, please review