Fix incorrect underlines rendering for empty lines in image editor.

Fixes #12807
Closes #12808

image-editor/lib/src/main/java/org/signal/imageeditor/core/renderers/MultiLineTextRenderer.java

@@ -333,6 +333,9 @@ public final class MultiLineTextRenderer extends InvalidateableRenderer implemen
         rendererContext.canvas.drawRoundRect(modeBounds, HIGHLIGHT_CORNER_RADIUS, HIGHLIGHT_CORNER_RADIUS, modePaint);
         modePaint.setAlpha(alpha);
       } else if (mode == Mode.UNDERLINE) {
+        if (text.isEmpty()) {
+          modeBounds.setEmpty();
+        } else {
           modeBounds.set(textBounds.left, selectionBounds.top, textBounds.right, selectionBounds.bottom);
           modeBounds.inset(-DimensionUnit.DP.toPixels(2), -DimensionUnit.DP.toPixels(2));
 
@@ -340,6 +343,7 @@ public final class MultiLineTextRenderer extends InvalidateableRenderer implemen
                          Math.max(modeBounds.top, modeBounds.bottom - DimensionUnit.DP.toPixels(6)),
                          modeBounds.right,
                          modeBounds.bottom - DimensionUnit.DP.toPixels(2));
+        }
 
         int alpha = modePaint.getAlpha();
         modePaint.setAlpha(rendererContext.getAlpha(alpha));