parsing.ts errors if a result does not have a locations property

The SARIF spec allows for a Result to omit the locations property (it says that results SHOULD include it, rather than SHALL or MUST include it). However, parsing.ts line 53 unconditionally runs const loc0 = r.locations[0] on all results it parses, and emits an error like this if there is a result with no locations property:

parsing.ts:50 Uncaught (in promise) TypeError: Cannot read property '0' of undefined
    at eval (parsing.ts:50)
    at Array.map (<anonymous>)
    at eval (parsing.ts:48)
    at Array.map (<anonymous>)
    at Object.parse (parsing.ts:31)
    at async eval (ResultsViewer.tsx:28)

The viewer should treat such results the same as it does results with an empty locations array.

Start in parsing.ts around line 53, then review the result handling used by ResultsViewer.tsx. Reproduce parsing with a SARIF result that omits locations and make it behave like a result with an empty locations array; done means no TypeError and the viewer continues to parse the result.