Fix getSkipSegmentsByHash requires valid json

The categories parameter has to be a valid array with strings in JSON format

src/routes/getSkipSegmentsByHash.ts

@@ -10,11 +10,23 @@ export async function getSkipSegmentsByHash(req: Request, res: Response) {
         return;
     }
 
-    const categories: Category[] = req.query.categories
-        ? JSON.parse(req.query.categories as string)
-        : req.query.category
-            ? [req.query.category]
-            : ['sponsor'];
+    let categories: Category[] = [];
+    try {
+        categories = req.query.categories
+            ? JSON.parse(req.query.categories as string)
+            : req.query.category
+                ? [req.query.category]
+                : ["sponsor"];
+        if (!Array.isArray(categories)) {
+            return res.status(400).send("Categories parameter does not match format requirements.");
+        }
+    }
+    catch(error) {
+        return res.status(400).send("Bad parameter: categories (invalid JSON)");
+    }
+    
+    // filter out none string elements, only flat array with strings is valid
+    categories = categories.filter((item: any) => typeof item === "string");
 
     // Get all video id's that match hash prefix
     const segments = getSegmentsByHash(req, hashPrefix, categories);