Merge #121: js: check for validity when analyzing a Miniscript

1f6c596 js: check for validity when analyzing a Miniscript (Antoine Poinsot)

Pull request description:

  I wanted to be more helpful if it's an issue with validty and output the first insane sub with no child, but we also accept invalid miniscripts there. So, at least just check for validity.

  I did not test this code.

ACKs for top commit:
  sipa:
    utACK 1f6c596

Tree-SHA512: bb119dfb822bc39e454de12c8e79d3425594197f42393ed5be06e71ff8bd8c739ef451a1fc719b48f4fbb36c8fbc8bb2fc7afae53285b7eeb924330c8526c96b

Author: sipa

js_bindings.cpp

@@ -119,7 +119,7 @@ void miniscript_analyze(const char* ms, char* costout, int costoutlen, char* asm
         str.erase(str.find_last_not_of(" \n\r\t") + 1);
         miniscript::NodeRef<std::string> ret;
         ret = miniscript::FromString(Expand(str), COMPILER_CTX);
-        if (!ret) {
+        if (!ret || !ret->IsValidTopLevel()) {
             Output("[analysis error]", costout, costoutlen);
             Output("[analysis error]", asmout, asmoutlen);
             return;