fix(white space): prevent duplicate blank lines from being added

closes #297.

src/djlint/formatter/condense.py

@@ -94,7 +94,7 @@ def condense_html(html: str, config: Config) -> str:
         for tag in [x.strip() for x in config.blank_line_after_tag.split(",")]:
             html = re.sub(
                 re.compile(
-                    rf"((?:{{%\s*?{tag}\b[^}}]+?%}}\n?)+)",
+                    rf"((?:{{%\s*?{tag}\b[^}}]+?%}}\n?)+)(?=[^\n])",
                     re.IGNORECASE | re.MULTILINE | re.DOTALL,
                 ),
                 func,

tests/test_config/test_blank_lines_after_tag/html_eight.html

@@ -0,0 +1,3 @@
+{% extends nothing %}
+
+<div></div>

tests/test_config/test_blank_lines_after_tag/test_config.py

@@ -2,7 +2,7 @@
 
 run::
 
-   pytest tests/test_config.py --cov=src/djlint --cov-branch \
+   pytest tests/test_config/test_blank_lines_after_tag/test_config.py --cov=src/djlint --cov-branch \
           --cov-report xml:coverage.xml --cov-report term-missing
 
 for a single test, run::
@@ -94,3 +94,14 @@ def test_blank_lines_after_tag(runner: CliRunner) -> None:
         ["tests/test_config/test_blank_lines_after_tag/html_seven.html", "--check"],
     )
     assert result.exit_code == 0
+
+    # check that multiple blank lines are not added
+    result = runner.invoke(
+        djlint,
+        [
+            "tests/test_config/test_blank_lines_after_tag/html_eight.html",
+            "--preserve-blank-lines",
+            "--check",
+        ],
+    )
+    assert result.exit_code == 0