Improve timingView with display of the ASS lines

Display the Ass lines on the timingView.

Allow for Drag & Drop of bars to change syl duration / line start and end time of the AssLineModels only (as changes are not written back to the Ass file yet).

src/Lib/Ass/AssFactory.cc

@@ -32,7 +32,6 @@ AssFactory::initFromStorage() noexcept
             }
         }
 
-        // Other lines
         else if (!currentSection.isEmpty()) {
             const int separatorIndex = line.indexOf(": ");
             const int baseValueIndex = separatorIndex + 2;
@@ -155,7 +154,7 @@ AssFactory::getStyle(const QString &name) const noexcept
         return StyleWeakPtr(*styleIt);
 
     // Will be unable to lock
-    return StyleWeakPtr(spareNullStylePtr);
+    return StyleWeakPtr();
 }
 
 bool