fix bug causing a warning message in Acrobat

CHANGELOG.md

@@ -18,6 +18,7 @@ This can also be enabled programmatically with `warnings.simplefilter('default',
 
 ## [2.7.9] - Not released yet
 ### Added
+* fix bug causing a warning message in Acrobat
 * support for overriding paragraph direction on bidirectional text
 * new optional `li_prefix_color` parameter for [`FPDF.write_html()`](https://py-pdf.github.io/fpdf2/fpdf/fpdf.html#fpdf.fpdf.FPDF.write_html)
 * support for `start` & `type` attributes of `<ol>` tags, and `type` attribute of `<ul>` tags, when using [`FPDF.write_html()`](https://py-pdf.github.io/fpdf2/fpdf/fpdf.html#fpdf.fpdf.FPDF.write_html)

fpdf/drawing.py

@@ -1445,9 +1445,7 @@ def serialize(self):
                 result[key] = value
 
         # There is additional logic in GraphicsContext to ensure that this will work
-        if (self.stroke_dash_pattern is not self.INHERIT) and (
-            self.stroke_dash_pattern is not None
-        ):
+        if self.stroke_dash_pattern and self.stroke_dash_pattern is not self.INHERIT:
             result[PDFStyleKeys.STROKE_DASH_PATTERN.value] = [
                 self.stroke_dash_pattern,
                 self.stroke_dash_phase,