added check for invalid source code

Author: DadeKuma

pages/index.tsx

@@ -18,7 +18,10 @@ const Home: NextPage = () => {
         setByteCode(() => data.byteCode);
         setAbi(() => JSON.stringify(data.abi));
       })
-      .catch(console.error)
+      .catch(err => {
+        alert(err);
+        console.error(err);
+      })
       .finally(() => {
         button.disabled = false;
       });

src/sol/compiler.ts

@@ -28,6 +28,10 @@ export const compile = (contractCode: string): Promise<ContractData[]> => {
         worker.onmessage = function (e: any) {
             const output = e.data.output;
             const result = [];
+            if (!output.contracts) {
+                reject("Invalid source code");
+                return;
+            }
             for (const contractName in output.contracts['contract']) {
                 const contract = output.contracts['contract'][contractName];
                 result.push({