assertion failure was a bit heavy-handed here. Raise error instead

src/crypt.zig

@@ -105,7 +105,11 @@ pub fn decryptWithKey(allocator: std.mem.Allocator, key: [key_size]u8, data: []c
     // deal with final block, PKCS#7 padding
     in = @ptrCast(*const [block_size]u8, data[(current_block * block_size)..(((current_block + 1) * block_size) - 1)]);
     ctx.decrypt(out[0..], in.*[0..]);
-    std.debug.assert(out[block_size - 1] <= block_size);
+    // Assertion was triggering when data was plain text
+    if (out[block_size - 1] > block_size) {
+        return error.DecryptionFailed;
+    }
+    // std.debug.assert(out[block_size - 1] <= block_size);
     try decrypted.appendSlice(out[0 .. block_size - out[block_size - 1]]);
     return decrypted.toOwnedSlice();
 }