timeline: fix timestamp binary search

Fixes dragging the mouse over bigger gaps of log activity making the red
position rectangle come out next to the mouse pointer. Also selects the proper
row now, not randomly 1-2 rows before or after the gap.

debug-viewer/GstDebugViewer/Plugins/Timeline.py

@@ -60,12 +60,12 @@ class LineFrequencySentinel (object):
         while True:
             middle = (last_index - first_index) // 2 + first_index
             if middle == first_index:
-                return last_index
+                return first_index
             ts = model_get (model_iter_nth_child (None, middle), col_id)
             if ts < target_ts:
-                first_index = middle + 1
+                first_index = middle
             elif ts > target_ts:
-                last_index = middle - 1
+                last_index = middle
             else:
                 return middle