[MIDI import] Tuplet recognition confused by larger quantization settings

Steps to reproduce bug
1. Open Harlem Nocturne.mid
2. Notice the correctly interpreted triplet rhythms in measures 20-21 (see quantize-to-default.png attached)
3. Change the Quantization value to "1/8" ("Eighth")
4. Uncheck "Reduce to shortest note in bar"
5. Click apply

Expected behavior: The measure should look similar to before, except the 16th rests would be quantized out. See quantize-to-8th-expected.PNG attached. (Possibly the 8th note triplet would be quantized to a regular 8th, but that is a matter for another discussion)

Actual behavior: Measures 20-21 have difficult to interpret (or nonsensical) tuplets (possible measure corruption since the beats don't seem to add up), and include 128th notes even though it is supposed to be quantized to 8th notes. See quantize-to-8th.png attached.

MuseScore version: c4e95c7

(Operating System: Windows 7)