Fixed error rendering Burmese text

Fixed an uncaught exception determining line break opportunities in Burmese text where a word is split down the middle at a word boundary.

src/symbol/shaping.ts

@@ -533,8 +533,10 @@ export function determineLineBreaks(
     let graphemeIndex = 0;
     for (const {index: wordIndex, segment: word} of wordSegmenter.segment(logicalInput.text)) {
         const graphemes = splitByGraphemeCluster(word);
+        let section;
         for (const grapheme of graphemes) {
-            const section = logicalInput.getSection(graphemeIndex);
+            // Grapheme cluster could be split across a word boundary. Fall back to the last known section.
+            section = logicalInput.getSection(graphemeIndex) || section;
             if (!!grapheme.trim()) {
                 currentX += getGlyphAdvance(grapheme, section, glyphMap, imagePositions, spacing, layoutTextSize);
             }