fix incorrect byte array comparison (#8379)

Fixes an exception when opening the code editor. `indexedDB.cmp` doesn't accept `undefined` values. Moved its usage to a separate function to guard against that.

app/gui2/src/stores/graph/graphDatabase.ts

@@ -1,7 +1,7 @@
 import { nonDictatedPlacement } from '@/components/ComponentBrowser/placement'
 import { SuggestionDb, groupColorStyle, type Group } from '@/stores/suggestionDatabase'
 import type { SuggestionEntry } from '@/stores/suggestionDatabase/entry'
-import { tryGetIndex } from '@/util/array'
+import { byteArraysEqual, tryGetIndex } from '@/util/array'
 import { Ast, AstExtended } from '@/util/ast'
 import { AliasAnalyzer } from '@/util/ast/aliasAnalysis'
 import { colorFromString } from '@/util/colors'
@@ -262,13 +262,13 @@ export class GraphDb {
         if (node == null) {
           this.nodeIdToNode.set(nodeId, newNode)
         } else {
-          if (indexedDB.cmp(node.pattern?.contentHash(), newNode.pattern?.contentHash())) {
+          if (!byteArraysEqual(node.pattern?.contentHash(), newNode.pattern?.contentHash())) {
             node.pattern = newNode.pattern
           }
           if (node.outerExprId !== newNode.outerExprId) {
             node.outerExprId = newNode.outerExprId
           }
-          if (indexedDB.cmp(node.rootSpan.contentHash(), newNode.rootSpan.contentHash()) !== 0) {
+          if (!byteArraysEqual(node.rootSpan.contentHash(), newNode.rootSpan.contentHash())) {
             node.rootSpan = newNode.rootSpan
           }
         }

app/gui2/src/util/array.ts

@@ -41,3 +41,11 @@ export function partitionPoint<T>(
 export function tryGetIndex<T>(arr: Opt<T[]>, index: Opt<number>): T | undefined {
   return index == null ? undefined : arr?.[index]
 }
+
+/**
+ * Check if two byte arrays have the same value. Allows optional values. If both inputs are `null`
+ * or `undefined`, the comparison also succeeds.
+ */
+export function byteArraysEqual(a: Opt<Uint8Array>, b: Opt<Uint8Array>): boolean {
+  return a === b || (a != null && b != null && indexedDB.cmp(a, b) === 0)
+}