Use is_empty

Clippy emits a couple of warnings of form:

  warning: length comparison to zero

As suggested, use `is_empty` instead of manually comparing to zero.

Author: tcharding

src/descriptor/key.rs

@@ -670,8 +670,7 @@ impl<K: InnerXKey> DescriptorXKey<K> {
             ),
         };
 
-        let path_excluding_wildcard = if self.wildcard != Wildcard::None && path.as_ref().len() > 0
-        {
+        let path_excluding_wildcard = if self.wildcard != Wildcard::None && !path.is_empty() {
             path.into_iter()
                 .take(path.as_ref().len() - 1)
                 .cloned()

src/interpreter/inner.rs

@@ -212,7 +212,7 @@ pub(super) fn from_txdata<'txin>(
             let has_annex = wit_stack
                 .last()
                 .and_then(|x| x.as_push().ok())
-                .map(|x| x.len() > 0 && x[0] == TAPROOT_ANNEX_PREFIX)
+                .map(|x| !x.is_empty() && x[0] == TAPROOT_ANNEX_PREFIX)
                 .unwrap_or(false);
             let has_annex = has_annex && (wit_stack.len() >= 2);
             if has_annex {