fix(query-builder): default missing builder arrays to [] to prevent traces explorer crash

A partial/legacy compositeQuery (shared link, old saved view) can omit
builder.queryFormulas / queryTraceOperator. QueryBuilderV2 rendered these
arrays directly and crashed the whole traces explorer (SIGNOZ-UI-5BA).

Normalize the arrays to [] where the query enters state
(useGetCompositeQueryParam and prepareQueryBuilderData) and optional-chain
the reads in QueryBuilderV2 as a render-level backstop.

frontend/src/components/QueryBuilderV2/QueryBuilderV2.tsx

@@ -241,28 +241,29 @@ export const QueryBuilderV2 = memo(function QueryBuilderV2({
 						))
 					)}
 
-					{!showOnlyWhereClause && currentQuery.builder.queryFormulas.length > 0 && (
-						<div className="qb-formulas-container">
-							{currentQuery.builder.queryFormulas.map((formula, index) => {
-								const query =
-									currentQuery.builder.queryData[index] ||
-									currentQuery.builder.queryData[0];
+					{!showOnlyWhereClause &&
+						currentQuery.builder.queryFormulas?.length > 0 && (
+							<div className="qb-formulas-container">
+								{currentQuery.builder.queryFormulas.map((formula, index) => {
+									const query =
+										currentQuery.builder.queryData[index] ||
+										currentQuery.builder.queryData[0];
 
-								return (
-									<div key={formula.queryName} className="qb-formula">
-										<Formula
-											filterConfigs={filterConfigs}
-											query={query}
-											formula={formula}
-											index={index}
-											isAdditionalFilterEnable={false}
-											isQBV2
-										/>
-									</div>
-								);
-							})}
-						</div>
-					)}
+									return (
+										<div key={formula.queryName} className="qb-formula">
+											<Formula
+												filterConfigs={filterConfigs}
+												query={query}
+												formula={formula}
+												index={index}
+												isAdditionalFilterEnable={false}
+												isQBV2
+											/>
+										</div>
+									);
+								})}
+							</div>
+						)}
 
 					{shouldShowFooter && (
 						<QueryFooter
@@ -290,7 +291,7 @@ export const QueryBuilderV2 = memo(function QueryBuilderV2({
 							</div>
 						))}
 
-						{currentQuery.builder.queryFormulas.map((formula) => (
+						{currentQuery.builder.queryFormulas?.map((formula) => (
 							<div key={formula.queryName} className="formula-name">
 								{formula.queryName}
 							</div>

frontend/src/components/QueryBuilderV2/QueryV2/__tests__/QueryV2.test.tsx

@@ -212,6 +212,32 @@ describe('QueryBuilderV2 + QueryV2 - base render', () => {
 		expect(handleRunQueryMock).toHaveBeenCalled();
 	});
 
+	it('does not crash when builder.queryFormulas/queryTraceOperator are missing (partial/legacy query)', () => {
+		const currentQueryBase = baseQBContext.currentQuery as Query;
+
+		mockedUseQueryBuilder.mockReturnValue({
+			...baseQBContext,
+			currentQuery: {
+				...currentQueryBase,
+				builder: {
+					queryData: currentQueryBase.builder.queryData,
+					queryFormulas: undefined as unknown as [],
+					queryTraceOperator: undefined as unknown as [],
+				},
+			},
+		});
+
+		expect(() =>
+			render(<QueryBuilderV2 panelType={PANEL_TYPES.TABLE} version="v4" />),
+		).not.toThrow();
+
+		// query list still renders from queryData, formulas block is skipped
+		expect(document.querySelector('.query-names-section')).toBeInTheDocument();
+		expect(
+			document.querySelector('.qb-formulas-container'),
+		).not.toBeInTheDocument();
+	});
+
 	it('fx button is disabled when functions already exist', () => {
 		const currentQueryBase = baseQBContext.currentQuery as Query;
 		const supersetQueryBase = baseQBContext.supersetQuery as Query;

frontend/src/hooks/queryBuilder/useGetCompositeQueryParam.ts

@@ -27,6 +27,14 @@ export const useGetCompositeQueryParam = (): Query | null => {
 				decodeURIComponent(compositeQuery.replace(/\+/g, ' ')),
 			);
 
+			// Add default values for optional fields if empty
+			if (parsedCompositeQuery?.builder) {
+				parsedCompositeQuery.builder.queryFormulas =
+					parsedCompositeQuery.builder.queryFormulas ?? [];
+				parsedCompositeQuery.builder.queryTraceOperator =
+					parsedCompositeQuery.builder.queryTraceOperator ?? [];
+			}
+
 			// Convert old format to new format for each query in builder.queryData
 			if (parsedCompositeQuery?.builder?.queryData) {
 				parsedCompositeQuery.builder.queryData =

frontend/src/providers/QueryBuilder.tsx

@@ -163,20 +163,23 @@ export function QueryBuilderProvider({
 	const prepareQueryBuilderData = useCallback(
 		(query: Query): Query => {
 			const builder: QueryBuilderData = {
-				queryData: query.builder.queryData?.map((item) => ({
-					...initialQueryBuilderFormValuesMap[
-						initialDataSource || DataSource.METRICS
-					],
-					...item,
-				})),
-				queryFormulas: query.builder.queryFormulas?.map((item) => ({
-					...initialFormulaBuilderFormValues,
-					...item,
-				})),
-				queryTraceOperator: query.builder.queryTraceOperator?.map((item) => ({
-					...initialQueryBuilderFormTraceOperatorValues,
-					...item,
-				})),
+				queryData:
+					query.builder.queryData?.map((item) => ({
+						...initialQueryBuilderFormValuesMap[
+							initialDataSource || DataSource.METRICS
+						],
+						...item,
+					})) ?? [],
+				queryFormulas:
+					query.builder.queryFormulas?.map((item) => ({
+						...initialFormulaBuilderFormValues,
+						...item,
+					})) ?? [],
+				queryTraceOperator:
+					query.builder.queryTraceOperator?.map((item) => ({
+						...initialQueryBuilderFormTraceOperatorValues,
+						...item,
+					})) ?? [],
 			};
 
 			const setupedQueryData = builder.queryData.map((item) => {