[FIX] compiler, components: allow empty slot

Before this commit, a t-set-slot that has no content was not even compiled, and thus not passed
to the component for which it has was defined

After this commit, we allow a t-set-slot to have no content (because it can have slot props)

src/compiler/code_generator.ts

@@ -1115,8 +1115,11 @@ export class CodeGenerator {
       let slotStr: string[] = [];
       for (let slotName in ast.slots) {
         const slotAst = ast.slots[slotName];
-        const name = this.compileInNewTarget("slot", slotAst.content, ctx, slotAst.on);
-        const params = [`__render: ${name}, __ctx: ${ctxStr}`];
+        const params = [];
+        if (slotAst.content) {
+          const name = this.compileInNewTarget("slot", slotAst.content, ctx, slotAst.on);
+          params.push(`__render: ${name}, __ctx: ${ctxStr}`);
+        }
         const scope = ast.slots[slotName].scope;
         if (scope) {
           params.push(`__scope: "${scope}"`);

src/compiler/parser.ts

@@ -118,7 +118,7 @@ export interface ASTTCall {
 }
 
 interface SlotDefinition {
-  content: AST;
+  content: AST | null;
   scope: string | null;
   on: EventHandlers | null;
   attrs: Attrs | null;
@@ -749,26 +749,24 @@ function parseComponent(node: Element, ctx: ParsingContext): AST | null {
       slotNode.removeAttribute("t-set-slot");
       slotNode.remove();
       const slotAst = parseNode(slotNode, ctx);
-      if (slotAst) {
-        let on: SlotDefinition["on"] = null;
-        let attrs: Attrs | null = null;
-        let scope: string | null = null;
-        for (let attributeName of slotNode.getAttributeNames()) {
-          const value = slotNode.getAttribute(attributeName)!;
-          if (attributeName === "t-slot-scope") {
-            scope = value;
-            continue;
-          } else if (attributeName.startsWith("t-on-")) {
-            on = on || {};
-            on[attributeName.slice(5)] = value;
-          } else {
-            attrs = attrs || {};
-            attrs[attributeName] = value;
-          }
+      let on: SlotDefinition["on"] = null;
+      let attrs: Attrs | null = null;
+      let scope: string | null = null;
+      for (let attributeName of slotNode.getAttributeNames()) {
+        const value = slotNode.getAttribute(attributeName)!;
+        if (attributeName === "t-slot-scope") {
+          scope = value;
+          continue;
+        } else if (attributeName.startsWith("t-on-")) {
+          on = on || {};
+          on[attributeName.slice(5)] = value;
+        } else {
+          attrs = attrs || {};
+          attrs[attributeName] = value;
         }
-        slots = slots || {};
-        slots[name] = { content: slotAst, on, attrs, scope };
       }
+      slots = slots || {};
+      slots[name] = { content: slotAst, on, attrs, scope };
     }
 
     // default slot