fix(@schematics/update): add check for invalid ranges

Fixes angular#12644

Author: tkrugg

packages/schematics/update/update/index.ts

@@ -33,6 +33,9 @@ type PeerVersionTransform = string | ((range: string) => string);
 // We export it to allow for testing.
 export function angularMajorCompatGuarantee(range: string) {
   range = semver.validRange(range);
+  if (range === null) {
+    return null;
+  }
   let major = 1;
   while (!semver.gtr(major + '.0.0', range)) {
     major++;