Attempt fix.

substrate/wasm-runtime/support/src/lib.rs

@@ -139,8 +139,12 @@ macro_rules! impl_stubs {
 			$(
 				#[no_mangle]
 				pub fn $name(input_data: *mut u8, input_len: usize) -> u64 {
-					let input = unsafe {
-						$crate::vec::Vec::from_raw_parts(input_data, input_len, input_len)
+					let input = if input_len == 0 {
+						$crate::vec::Vec::new()
+					} else {
+						unsafe {
+							$crate::vec::Vec::from_raw_parts(input_data, input_len, input_len)
+						}
 					};
 
 					let output = super::$name(&input[..]);

substrate/wasm-runtime/test/src/lib.rs

@@ -54,8 +54,6 @@ fn test_panic(_input: &[u8]) -> Vec<u8> {
 fn test_conditional_panic(input: &[u8]) -> Vec<u8> {
 	if input.len() > 0 {
 		panic!("test panic");
-	} else {
-		assert!(input.len() > 0);
 	}
 	input.to_vec()
 }