Fix NPE in DefectMissing for range +unlint of absent lint (#841)

src/main/java/org/eolang/lints/DefectMissing.java

@@ -44,7 +44,11 @@ public Boolean apply(final String unlint) {
         final String name = split[0];
         final List<Integer> lines = this.defects.get(name);
         if (unlint.matches(String.format("%s:\\d+-\\d+", name))) {
-            missing = !lines.stream().allMatch(new UnlintInRange(unlint));
+            if (lines == null) {
+                missing = !this.excluded.contains(name);
+            } else {
+                missing = !lines.stream().allMatch(new UnlintInRange(unlint));
+            }
         } else {
             final Set<String> names;
             if (this.defects != null) {

src/test/java/org/eolang/lints/DefectMissingTest.java

@@ -80,4 +80,23 @@ void returnsTrueIfSomeLineIsOutOfRange() {
             Matchers.equalTo(true)
         );
     }
+
+    @Test
+    void returnsTrueWhenRangeReferencesAbsentLint() {
+        MatcherAssert.assertThat(
+            "Defect should be missing when referenced lint is absent from map",
+            new DefectMissing(new MapOf<>("other-lint", new ListOf<>(1, 2)), new ListOf<>())
+                .apply("ascii-only:1-5"),
+            Matchers.equalTo(true)
+        );
+    }
+
+    @Test
+    void returnsTrueWhenRangeReferencesLintInEmptyMap() {
+        MatcherAssert.assertThat(
+            "Defect should be missing when defects map is empty",
+            new DefectMissing(new MapOf<>(), new ListOf<>()).apply("ascii-only:1-5"),
+            Matchers.equalTo(true)
+        );
+    }
 }

src/test/java/org/eolang/lints/LtUnlintNonExistingDefectTest.java

@@ -222,4 +222,26 @@ void catchesUnlintWithOutOfRangeLines() throws IOException {
             Matchers.iterableWithSize(1)
         );
     }
+
+    @Test
+    void catchesRangeUnlintOfAbsentLint() throws IOException {
+        MatcherAssert.assertThat(
+            "Range unlint referencing an absent lint should be reported, not throw NPE",
+            new LtUnlintNonExistingDefect(
+                new ListOf<>(new LtAsciiOnly()),
+                new ListOf<>()
+            ).defects(
+                new EoSyntax(
+                    String.join(
+                        "\n",
+                        "+unlint ascii-only:1-5",
+                        "",
+                        "# Hello.",
+                        "[] > main"
+                    )
+                ).parsed()
+            ),
+            Matchers.hasSize(Matchers.greaterThan(0))
+        );
+    }
 }