Merge branch 'master' of https://github.com/xtermjs/xterm.js into fix-underline-color

src/renderer/atlas/DynamicCharAtlas.ts

@@ -94,7 +94,7 @@ export default class DynamicCharAtlas extends BaseCharAtlas {
   ): boolean {
     const glyphKey = getGlyphCacheKey(glyph);
     const cacheValue = this._cacheMap.get(glyphKey);
-    if (cacheValue != null) {
+    if (cacheValue !== null && cacheValue !== undefined) {
       this._drawFromCache(ctx, cacheValue, x, y);
       return true;
     } else if (this._canCache(glyph) && this._drawToCacheCount < FRAME_CACHE_DRAW_LIMIT) {

src/renderer/atlas/StaticCharAtlas.ts

@@ -53,7 +53,7 @@ export default class StaticCharAtlas extends BaseCharAtlas {
     y: number
   ): boolean {
     // we're not warmed up yet
-    if (this._texture == null) {
+    if (this._texture === null || this._texture === undefined) {
       return false;
     }