Conform more code to strict null checking (#10169)

* Conform more code to strict null checking

* delint

* Iterate

* delint

* Fix bad test

src/editor/dom.ts

@@ -190,6 +190,8 @@ function getTextAndOffsetToNode(editor: HTMLDivElement, selectionNode: Node): {
 // get text value of text node, ignoring ZWS if it's a caret node
 function getTextNodeValue(node: Node): string {
     const nodeText = node.nodeValue;
+    if (!nodeText) return "";
+
     // filter out ZWS for caret nodes
     if (isCaretNode(node.parentElement)) {
         // typed in the caret node, so there is now something more in it than the ZWS
@@ -200,9 +202,9 @@ function getTextNodeValue(node: Node): string {
             // only contains ZWS, which is ignored, so return empty string
             return "";
         }
-    } else {
-        return nodeText;
     }
+
+    return nodeText;
 }
 
 export function getRangeForSelection(editor: HTMLDivElement, model: EditorModel, selection: Selection): Range {

src/editor/parts.ts

@@ -424,7 +424,7 @@ class RoomPillPart extends PillPart {
         let initialLetter = "";
         let avatarUrl = Avatar.avatarUrlForRoom(this.room, 16, 16, "crop");
         if (!avatarUrl) {
-            initialLetter = Avatar.getInitialLetter(this.room?.name || this.resourceId);
+            initialLetter = Avatar.getInitialLetter(this.room?.name || this.resourceId) ?? "";
             avatarUrl = Avatar.defaultAvatarUrlForString(this.room?.roomId ?? this.resourceId);
         }
         this.setAvatarVars(node, avatarUrl, initialLetter);
@@ -478,7 +478,7 @@ class UserPillPart extends PillPart {
         const avatarUrl = Avatar.avatarUrlForMember(this.member, 16, 16, "crop");
         let initialLetter = "";
         if (avatarUrl === defaultAvatarUrl) {
-            initialLetter = Avatar.getInitialLetter(name);
+            initialLetter = Avatar.getInitialLetter(name) ?? "";
         }
         this.setAvatarVars(node, avatarUrl, initialLetter);
     }