Handle empty (null) query result without crashing

stackql emits the literal `null` for a query that matches no rows. assertResult
parsed that to null and then read `.length` on it, throwing
"Cannot read properties of null (reading 'length')" instead of reporting a
clean assertion failure. Normalise a non-array parsed result to an empty array
so a 0-rows-vs-expected case fails with a readable message. Adds coverage.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: jeffreyaven

lib/assert.js

@@ -56,7 +56,11 @@ function assertResult(core) {
     // if no EXPECTED_RESULTS_STR, EXPECTED_RESULTS_FILE_PATH or EXPECTED_ROWS, fail the action
     if (!EXPECTED_RESULTS_STR && !EXPECTED_RESULTS_FILE_PATH && !EXPECTED_ROWS) throw new Error("❌ Cannot find expected result, file path or expected rows");
 
-    const actualResult = parseResult(RESULT);
+    // stackql emits the literal `null` for a query that matches no rows;
+    // normalise that (and any non-array result) to an empty array so an
+    // empty result set is a clean assertion failure, not a crash on .length.
+    const parsed = parseResult(RESULT);
+    const actualResult = Array.isArray(parsed) ? parsed : [];
 
     core.info("🔍 Checking results...");
 

lib/tests/assert.test.js

@@ -185,6 +185,17 @@ describe('assertResult', ()=>{
         expect(coreObj.info).toHaveBeenCalledWith(expect.stringContaining('StackQL Assert Successful'))
     })
 
+    it('it should fail cleanly (not crash) when the query returns null and rows are expected', ()=>{
+        // stackql emits the literal `null` for an empty result set
+        process.env.RESULT = 'null'
+        process.env.EXPECTED_RESULTS_STR = undefined;
+        process.env.EXPECTED_RESULTS_FILE_PATH = undefined;
+        process.env.EXPECTED_ROWS = 1
+
+        assertResult(coreObj)
 
+        expect(coreObj.setFailed).toHaveBeenCalledWith(expect.stringContaining('StackQL Assert Failed'))
+        expect(coreObj.error).toHaveBeenCalledWith('Expected rows: 1, got: 0')
+    })
 
 })