cmMakefile: Invert if() condition to remove else

Source/cmMakefile.cxx

@@ -1249,13 +1249,13 @@ void cmMakefile::AddLinkDirectoryForTarget(const std::string& target,
                                            const std::string& d)
 {
   cmTargets::iterator i = this->Targets.find(target);
-  if (i != this->Targets.end()) {
-    i->second.AddLinkDirectory(d);
-  } else {
+  if (i == this->Targets.end()) {
     cmSystemTools::Error(
       "Attempt to add link directories to non-existent target: ",
       target.c_str(), " for directory ", d.c_str());
+    return;
   }
+  i->second.AddLinkDirectory(d);
 }
 
 void cmMakefile::InitializeFromParent(cmMakefile* parent)