Avoid printing a stack trace when there is no resultsPath

I don't know exactly when this can happen, but a customer has just
shown me a stack trace like this:

```
TypeError: Cannot destructure property 'resultsPath' of 'resultsPaths' as it is undefined.
    at Object.interpretResults (/xxx/.vscode/extensions/github.vscode-codeql-1.4.5/out/query-results.js:120:13)
    at InterfaceManager._getInterpretedResults (/xxx/.vscode/extensions/github.vscode-codeql-1.4.5/out/interface.js:377:45)
    at InterfaceManager.showResultsAsDiagnostics (/xxx/.vscode/extensions/github.vscode-codeql-1.4.5/out/interface.js:447:43)
    at runMicrotasks (<anonymous>)
    at processTicksAndRejections (internal/process/task_queues.js:97:5)
    at async InterfaceManager.handleMsgFromView (/xxx/.vscode/extensions/github.vscode-codeql-1.4.5/out/interface.js:151:29)
```

This commit will avoid printing this stack trace and instead print
a more descriptive message to the logs.

Author: aeisenberg

extensions/ql-vscode/src/interface.ts

@@ -554,24 +554,26 @@ export class InterfaceManager extends DisposableObject {
     sourceInfo: cli.SourceInfo | undefined,
     sourceLocationPrefix: string,
     sortState: InterpretedResultsSortState | undefined
-  ): Promise<Interpretation> {
+  ): Promise<Interpretation | undefined> {
+    if (!resultsPaths) {
+      this.logger.log('No results path. Cannot display interpreted results.');
+      return undefined;
+    }
+
     const sarif = await interpretResults(
       this.cliServer,
       metadata,
       resultsPaths,
       sourceInfo
     );
+
     sarif.runs.forEach(run => {
       if (run.results !== undefined) {
         sortInterpretedResults(run.results, sortState);
       }
     });
 
-    const numTotalResults = (() => {
-      if (sarif.runs.length === 0) return 0;
-      if (sarif.runs[0].results === undefined) return 0;
-      return sarif.runs[0].results.length;
-    })();
+    const numTotalResults = sarif.runs[0]?.results?.length || 0;
 
     const interpretation: Interpretation = {
       sarif,
@@ -673,6 +675,10 @@ export class InterfaceManager extends DisposableObject {
       undefined
     );
 
+    if (!interpretation) {
+      return;
+    }
+
     try {
       await this.showProblemResultsAsDiagnostics(interpretation, database);
     } catch (e) {