fix: add emptyset as lhs fallback (#10)

Author: WhySoBad

frontend/src/lib/components/exerciseListElement.tsx

@@ -61,7 +61,7 @@ const ExerciseListElment = ({ exercise }: exerciseListElementProps) => {
         </Grid.Col>
         <Grid.Col span={1}>
           <Group justify="flex-end" gap={0}>
-            <Tooltip label="toggle">
+            <Tooltip label={fav ? "Remove from favorites" : "Add to favorites"}>
               <ActionIcon
                 variant={"transparent"}
                 onClick={() => {

frontend/src/lib/components/feedback.tsx

@@ -101,7 +101,7 @@ const Feedback = ({ exercise }: FeedbackProps) => {
             size={10}
             color={color}
           />
-          <Button onClick={onSubmit}>Submit</Button>
+          <Button onClick={onSubmit} disabled={like === undefined}>Submit</Button>
         </Stack>
       </Drawer>
     </>

frontend/src/lib/components/header.tsx

@@ -8,7 +8,6 @@ const Header: React.FC = (): React.ReactNode => {
   return (
     <Flex px={"md"} align="center" justify="space-between" h="100%">
       <Link
-        onClick={location.reload}
         href={"/"}
         style={{ textDecoration: "none", color: "inherit" }}
       >

frontend/src/lib/utils/export.ts

@@ -11,7 +11,7 @@ export function exportToTypst(root: NodeType, nodes: Array<NodeType>): string {
 
 function exportSubformula(node: NodeType, nodes: Array<NodeType>): string {
   const name = getTypstRuleByName(node.rule as Rules);
-  const lhs = node.statement.lhs.map(formulaToTypst).join(", ");
+  const lhs = node.statement.lhs.map(formulaToTypst).join(", ") || "emptyset";
   const current = formulaToTypst(node.statement.formula);
 
   const premisses = node.premisses