Fix a crash in the new dependency check

Fixes #697
Fixes #696

Author: sindresorhus

Diff for: source/util.js

@@ -89,8 +89,8 @@ export const getNewDependencies = async (newPkg, rootDir) => {
 
 	const newDependencies = [];
 
-	for (const dependency of Object.keys(newPkg.dependencies)) {
-		if (!oldPkg.dependencies[dependency]) {
+	for (const dependency of Object.keys(newPkg.dependencies ?? {})) {
+		if (!oldPkg.dependencies?.[dependency]) {
 			newDependencies.push(dependency);
 		}
 	}

Diff for: source/version.js

@@ -58,9 +58,17 @@ export default class Version {
 	}
 
 	static verifyRequirementSatisfied(dependency, version) {
-		const depRange = pkg.engines[dependency];
-		if (!new Version(version).satisfies(depRange)) {
-			throw new Error(`Please upgrade to ${dependency}${depRange}`);
+		if (!pkg.engines?.node) {
+			throw new Error('Please include a `engines.node` field in your package.json');
+		}
+
+		const versionRange = pkg.engines?.[dependency];
+		if (!versionRange) {
+			return;
+		}
+
+		if (!new Version(version).satisfies(versionRange)) {
+			throw new Error(`Please upgrade to ${dependency}${versionRange}`);
 		}
 	}