Fix 'err:parameter node not found' for dotted reference

[AdrieVanDijk]

I had a problem with a harbor webhook
Part of the payload sent by the IMAGE SCAN COMPLETED notification, is:

         "scan_overview": {
           "application/vnd.scanner.adapter.vuln.report.harbor+json; version=1.0": {
             "complete_percent": 100,
             "duration": 42,

             "end_time": "2021-01-22T20:27:27.404922Z",
             "report_id": "87962b6f-589c-4dbf-9972-2646cae2cee4",
             "scan_status": "Success",
             "scanner": {
               "name": "Trivy",
               "vendor": "Aqua Security",
               "version": "v0.9.2"
             },
             "severity": "Medium",
             "start_time": "2021-01-22T20:26:45.096622Z",
             "summary": {
               "fixable": 6,
               "summary": {
                 "Low": 21,
                 "Medium": 7
               },
               "total": 28
             }
           }
         },

In order to extract the "Severity" i have to use the path:

scan_overview.application/vnd.scanner.adapter.vuln.report.harbor+json; version=1.0.severity

This gave error "parameter node not found', because paths with dotted references only worked when the reference with the dots was at the end of the path.
This change fixes that.