Fix keyword completion silently returning zero suggestions

Curated supplemental keywords (STORE, AIM, CVTYPE, AMF, PREFT,
ZCRITVIS, SPECHA, SPECHB, SPECHG, SPECHH) were merged into the
runtime index without a sections array, even though several call
sites (including the completion provider's item.detail) access
entry.sections unconditionally. Hitting any of these 10 keywords
during Array.map aborted the entire keyword-name completion list
for every prefix, since a thrown callback discards all results.

Default sections to [] when merging the supplement so every entry
satisfies the sections: string[] contract.

Author: magnesj

vscode-extension/src/keyword-supplement.ts

@@ -66,7 +66,8 @@ export const SUPPLEMENTAL_KEYWORDS: AnalysisIndex = {
 export function applyKeywordSupplement(index: AnalysisIndex): AnalysisIndex {
   for (const name in SUPPLEMENTAL_KEYWORDS) {
     if (index[name] === undefined) {
-      index[name] = SUPPLEMENTAL_KEYWORDS[name] as AnalysisEntry;
+      const entry = SUPPLEMENTAL_KEYWORDS[name] as AnalysisEntry;
+      index[name] = { sections: [], ...entry };
     }
   }
   return index;