Error when checking non-const dependency expression

[duncanbeevers]

I added this test-case that demonstrates the error. When examining a useCallback or useMemo dependency defined not as a const, but as a let with no init value, the getIdentifierMemoStatus method fails.

diff --git a/__tests__/require-usememo.ts b/__tests__/require-usememo.ts
index cbe60de..fe24d0c 100644
--- a/__tests__/require-usememo.ts
+++ b/__tests__/require-usememo.ts
@@ -142,5 +142,13 @@ ruleTester.run("useMemo", rule, {
       options: [{ strict: true }],
       errors: [{ messageId: "unknown-usememo-props" }],
     },
+    {
+      code: `const Component = () => {
+        let myObject;
+        myObject = {};
+        return <Child prop={myObject} />;
+      }`,
+      errors: [{ messageId: "object-usememo-props" }],
+    },
   ],
 });

OUTPUT

  ● useMemo › invalid › const Component = () => {
        let myObject;
        myObject = {};
        return <Child prop={myObject} />;
      }

    TypeError: Cannot read property 'type' of null
    Occurred while linting <input>:4

      62 |   expression: TSESTree.Expression
      63 | ): MemoStatus {
    > 64 |   switch (expression.type) {
         |                      ^
      65 |     case "ObjectExpression":
      66 |       return MemoStatus.UnmemoizedObject;
      67 |     case "ArrayExpression":

      at getExpressionMemoStatus (common.ts:64:22)
      at getIdentifierMemoStatus (common.ts:57:10)
      at Object.getExpressionMemoStatus (common.ts:85:14)
      at JSXAttribute (require-usememo.ts:81:21)
      at node_modules/eslint/lib/linter/safe-emitter.js:45:58
          at Array.forEach (<anonymous>)
      at Object.emit (node_modules/eslint/lib/linter/safe-emitter.js:45:38)
      at NodeEventGenerator.applySelector (node_modules/eslint/lib/linter/node-event-generator.js:256:26)
      at NodeEventGenerator.applySelectors (node_modules/eslint/lib/linter/node-event-generator.js:285:22)
      at NodeEventGenerator.enterNode (node_modules/eslint/lib/linter/node-event-generator.js:299:14)