Fix counting of resolvable outdated packages (#2420)

diff --git a/lib/src/command/outdated.dart b/lib/src/command/outdated.dart
index 56a8208..c5978d6 100644
--- a/lib/src/command/outdated.dart
+++ b/lib/src/command/outdated.dart
@@ -333,8 +333,10 @@
       .length;
 
   var notAtResolvable = rows
-      .where(
-          (row) => row.resolvable != null && row.upgradable != row.resolvable)
+      .where((row) =>
+          row.current != null &&
+          row.resolvable != null &&
+          row.upgradable != row.resolvable)
       .length;
 
   if (upgradable != 0) {
diff --git a/test/outdated/goldens/newer_versions.txt b/test/outdated/goldens/newer_versions.txt
index ea2f04d..bdd3548 100644
--- a/test/outdated/goldens/newer_versions.txt
+++ b/test/outdated/goldens/newer_versions.txt
@@ -58,7 +58,7 @@
 3 upgradable dependencies are locked (in pubspec.lock) to older versions.
 To update these dependencies, use `pub upgrade`.
 
-4  dependencies are constrained to versions that are older than a resolvable version.
+2  dependencies are constrained to versions that are older than a resolvable version.
 To update these dependencies, edit pubspec.yaml.
 
 $ pub outdated --no-color --mark=none
@@ -79,7 +79,7 @@
 3 upgradable dependencies are locked (in pubspec.lock) to older versions.
 To update these dependencies, use `pub upgrade`.
 
-4  dependencies are constrained to versions that are older than a resolvable version.
+2  dependencies are constrained to versions that are older than a resolvable version.
 To update these dependencies, edit pubspec.yaml.
 
 $ pub outdated --no-color --up-to-date
@@ -102,7 +102,7 @@
 3 upgradable dependencies are locked (in pubspec.lock) to older versions.
 To update these dependencies, use `pub upgrade`.
 
-4  dependencies are constrained to versions that are older than a resolvable version.
+2  dependencies are constrained to versions that are older than a resolvable version.
 To update these dependencies, edit pubspec.yaml.
 
 $ pub outdated --no-color --pre-releases
@@ -123,7 +123,7 @@
 3 upgradable dependencies are locked (in pubspec.lock) to older versions.
 To update these dependencies, use `pub upgrade`.
 
-4  dependencies are constrained to versions that are older than a resolvable version.
+2  dependencies are constrained to versions that are older than a resolvable version.
 To update these dependencies, edit pubspec.yaml.
 
 $ pub outdated --no-color --no-dev-dependencies