fix(svg): drop SVG icon layers with no drawing segment

CHANGELOG.md

@@ -228,6 +228,14 @@ Entries land here as they merge.
 
 ### Bug fixes
 
+- **A stray non-drawing element no longer breaks a whole SVG icon.** A
+  visible-painted SVG element that lowers to a moveto-only or moveto+close
+  path — `d="M12 12"`, a zero-length arc, the stray subpaths real exporters
+  emit — drew no ink, yet a lone moveto threw at `SvgIcon#node(...)` (an empty
+  `PathNode`) and a moveto+close rendered blank. `SvgIconReader` now drops a
+  layer with no drawing segment, so one degenerate element no longer fails the
+  icon; an icon of only such elements still fails loudly with "no drawable
+  geometry".
 - **Stacked bars anchor at zero even with an explicit positive axis minimum.**
   A stacked bar chart with `valueAxis().min(positive)` lifted the baseline
   while segment heights stayed measured from zero, so the stack overshot its

src/main/java/com/demcha/compose/document/svg/SvgIconReader.java

@@ -192,6 +192,13 @@ private static void emitLayer(Element element, String d, Paint paint,
             return;
         }
         SvgPath geometry = SvgPath.parseTransformed(d, matrix, box[0], box[1], box[2], box[3]);
+        if (!geometry.hasDrawingSegment()) {
+            // A moveto-only or moveto+close element (e.g. d="M12 12", or a
+            // zero-length arc that lowers to a lone moveto) draws no ink. Drop
+            // it so one degenerate element a real-world exporter emitted does
+            // not fail the whole icon at SvgIcon#node(...).
+            return;
+        }
 
         // Gradients resolve here, where the shape's geometry (the
         // objectBoundingBox reference) and accumulated affine exist. The flat

src/main/java/com/demcha/compose/document/svg/SvgPath.java

@@ -154,6 +154,25 @@ public double aspectRatio() {
         return sourceWidth / sourceHeight;
     }
 
+    /**
+     * Whether this path actually draws ink: it carries at least one
+     * {@code lineTo} / {@code cubicTo} after the leading {@code moveTo}. A
+     * moveto-only path, or a moveto followed only by {@code close} (which a
+     * degenerate SVG element such as {@code d="M12 12"} or a zero-length arc
+     * lowers to), draws nothing.
+     *
+     * @return {@code true} if a drawing segment is present
+     */
+    boolean hasDrawingSegment() {
+        for (DocumentPathSegment segment : segments) {
+            if (segment instanceof DocumentPathSegment.LineTo
+                    || segment instanceof DocumentPathSegment.CubicTo) {
+                return true;
+            }
+        }
+        return false;
+    }
+
     // ------------------------------------------------------------------
     // Normalization (y-flip into the unit box)
     // ------------------------------------------------------------------

src/test/java/com/demcha/compose/document/svg/SvgIconTest.java

@@ -67,6 +67,35 @@ void invisibleElementsProduceNoLayers() {
         assertThat(icon.layers()).hasSize(1);
     }
 
+    @Test
+    void degenerateGeometryIsDroppedSoOneStrayElementDoesNotFailTheIcon() {
+        // Real exporters emit stray moveto-only / moveto+close subpaths that
+        // draw nothing. They must not break the whole icon: a lone moveto used
+        // to throw at node() (an empty PathNode), a moveto+close rendered blank.
+        SvgIcon icon = SvgIcon.parse("""
+                <svg viewBox="0 0 10 10">
+                  <path d="M5 5" fill="#000"/>
+                  <path d="M5 5 Z" fill="#000"/>
+                  <path d="M0 0 H10 V10 Z" fill="#f00"/>
+                </svg>
+                """);
+
+        // Only the drawable box survives; both degenerate paths are dropped.
+        assertThat(icon.layers()).hasSize(1);
+        assertThat(icon.node(24)).isNotNull();   // threw before the drop guard
+    }
+
+    @Test
+    void anIconOfOnlyDegenerateGeometryFailsLoudly() {
+        assertThatThrownBy(() -> SvgIcon.parse("""
+                <svg viewBox="0 0 10 10">
+                  <path d="M5 5" fill="#000"/>
+                </svg>
+                """))
+                .isInstanceOf(IllegalArgumentException.class)
+                .hasMessageContaining("no drawable geometry");
+    }
+
     @Test
     void basicShapesLowerToPathGeometry() {
         SvgIcon icon = SvgIcon.parse("""