fix: don't panic if there is a version requirement without version (#262)

Author: Byron

cargo-smart-release/src/command/release/manifest.rs

@@ -543,7 +543,8 @@ fn set_version_and_update_package_dependency(
                     let version_req = VersionReq::parse(current_version_req.as_str().expect("versions are strings"))?;
                     let force_update = conservative_pre_release_version_handling
                         && version::is_pre_release(new_version) // setting the lower bound unnecessarily can be harmful
-                        && !version::rhs_is_breaking_bump_for_lhs(&req_as_version(&version_req), new_version); // don't claim to be conservative if this is necessary anyway
+                        // don't claim to be conservative if this is necessary anyway
+                        && req_as_version(&version_req).map(|req_version|!version::rhs_is_breaking_bump_for_lhs(&req_version, new_version)).unwrap_or(false);
                     if !version_req.matches(new_version) || force_update {
                         if !version_req_unset_or_default(&version_req) {
                             bail!(
@@ -577,13 +578,12 @@ fn set_version_and_update_package_dependency(
     Ok(manifest != new_manifest)
 }
 
-fn req_as_version(req: &VersionReq) -> Version {
-    let comp = &req.comparators.get(0).expect("at least one version comparator");
-    Version {
+fn req_as_version(req: &VersionReq) -> Option<Version> {
+    req.comparators.get(0).map(|comp| Version {
         major: comp.major,
         minor: comp.minor.unwrap_or(0),
         patch: comp.patch.unwrap_or(0),
         pre: comp.pre.clone(),
         build: Default::default(),
-    }
+    })
 }