Fix for bug 124209 (Deleting selection in plain text reply compose causes hang)

and bug 124375 (composer / editor hang when delete blank lines)

Allow start/end points to be set to empty text nodes to prevent
infinite loop.

r=glazman@netscape.com  sr=sfraser@netscape.com,shaver@mozilla.org

editor/libeditor/html/nsWSRunObject.cpp

@@ -748,6 +748,15 @@ nsWSRunObject::GetWSNodes()
         PRInt32 len;
         res = textNode->GetTextLength(&len);
         NS_ENSURE_SUCCESS(res, res);
+
+        if (len < 1)
+        {
+          // Zero length text node. Set start point to it
+          // so we can get past it!
+          start.SetPoint(priorNode,0);
+        }
+        else
+        {
           PRInt32 pos;
           for (pos=len-1; pos>=0; pos--)
           {
@@ -774,6 +783,7 @@ nsWSRunObject::GetWSNodes()
             start.SetPoint(priorNode,pos);
           }
         }
+      }
       else
       {
         // it's a break or a special node, like <img>, that is not a block and not
@@ -859,6 +869,15 @@ nsWSRunObject::GetWSNodes()
         PRInt32 len;
         res = textNode->GetTextLength(&len);
         NS_ENSURE_SUCCESS(res, res);
+
+        if (len < 1)
+        {
+          // Zero length text node. Set end point to it
+          // so we can get past it!
+          end.SetPoint(nextNode,0);
+        }
+        else
+        {
           PRInt32 pos;
           for (pos=0; pos<len; pos++)
           {
@@ -885,6 +904,7 @@ nsWSRunObject::GetWSNodes()
             end.SetPoint(nextNode,pos+1);
           }
         }
+      }
       else
       {
         // we encountered a break or a special node, like <img>,