[compiler] Avoid empty switch cases (#33625)

Small cosmetic win, found this when i was looking at some code
internally with lots of cases that all share the same logic. Previously,
all the but last one would have an empty block.

---
[//]: # (BEGIN SAPLING FOOTER)
Stack created with [Sapling](https://sapling-scm.com). Best reviewed
with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33625).
* #33643
* #33642
* #33640
* __->__ #33625
* #33624

compiler/packages/babel-plugin-react-compiler/src/ReactiveScopes/CodegenReactiveFunction.ts

@@ -1181,7 +1181,7 @@ function codegenTerminal(
               ? codegenPlaceToExpression(cx, case_.test)
               : null;
           const block = codegenBlock(cx, case_.block!);
-          return t.switchCase(test, [block]);
+          return t.switchCase(test, block.body.length === 0 ? [] : [block]);
         }),
       );
     }

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/block-scoping-switch-variable-scoping.expect.md

@@ -50,8 +50,7 @@ function Component(props) {
       console.log(handlers.value);
       break bb0;
     }
-    default: {
-    }
+    default:
   }
 
   t0 = handlers;

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/dominator.expect.md

@@ -67,8 +67,7 @@ function Component(props) {
     case "b": {
       break bb1;
     }
-    case "c": {
-    }
+    case "c":
     default: {
       x = 6;
     }

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/reverse-postorder.expect.md

@@ -50,10 +50,8 @@ function Component(props) {
       case 1: {
         break bb0;
       }
-      case 2: {
-      }
-      default: {
-      }
+      case 2:
+      default:
     }
   } else {
     if (props.cond2) {

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/ssa-switch.expect.md

@@ -41,8 +41,7 @@ function foo() {
     case 2: {
       break bb0;
     }
-    default: {
-    }
+    default:
   }
 }
 

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/switch-with-fallthrough.expect.md

@@ -43,22 +43,17 @@ export const FIXTURE_ENTRYPOINT = {
 ```javascript
 function foo(x) {
   bb0: switch (x) {
-    case 0: {
-    }
-    case 1: {
-    }
+    case 0:
+    case 1:
     case 2: {
       break bb0;
     }
     case 3: {
       break bb0;
     }
-    case 4: {
-    }
-    case 5: {
-    }
-    default: {
-    }
+    case 4:
+    case 5:
+    default:
   }
 }