fix(manager/nuget): Skip dep if version is undefined (#16757)

lib/modules/manager/nuget/__fixtures__/sample.csproj

@@ -34,6 +34,7 @@
     <PackageReference Include="NotUpdatable3" Version="(1.2.3, 3.2.1)" />
     <PackageReference Include="NotUpdatable3" Version="[1.2.3, 3.2.1]" />
     <PackageReference Include="NotUpdatable3" Version="[1.2.3, 3.2.1)" />
+    <PackageReference Include="NotUpdatable3" />
   </ItemGroup>
   <ItemGroup>
     <DotNetCliToolReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Tools" Version="1.0.0" />

lib/modules/manager/nuget/extract.ts

+import is from '@sindresorhus/is';
 import { XmlDocument, XmlElement, XmlNode } from 'xmldoc';
 import { logger } from '../../../logger';
 import { getSiblingFileName, localPathExists } from '../../../util/fs';
@@ -48,10 +49,9 @@ function extractDepsFromXml(xmlNode: XmlDocument): PackageDependency[] {
         child.valueWithPath('Version') ??
         attr?.VersionOverride ??
         child.valueWithPath('VersionOverride');
-      const currentValue = checkVersion
-
-        ?.exec(version)
-        ?.groups?.currentValue?.trim();
+      const currentValue = is.nonEmptyStringAndNotWhitespace(version)
+        ? checkVersion.exec(version)?.groups?.currentValue?.trim()
+        : undefined;
       if (depName && currentValue) {
         results.push({
           datasource: NugetDatasource.id,