[FM] Only space character should not be allowed while renaming a FM channel or...

[FM] Only space character should not be allowed while renaming a FM channel or a recorded audio file

Launch FM app and plug in a wired headset -> Star mark a channel
to add it favorite -> Go to favorite, tap on the menu (3 dots) and
tap on rename to rename the channel -> Enter only spaces and save
the channel -> Record an audio and on the dialogue, rename it with
only spaces and tap on save, the channel names and audio files are
saved without any error message. While playing this channel, FM
notification shows no name because of the spaces

The fix is to add some condition check for showing/hiding save button.

Bug 19087268
from: https://partner-android-review.googlesource.com/#/c/198815/



Change-Id: I2ac0b81d2311eace3d5e28baca31d59d3095c8d1
Signed-off-by: Benson Huang <benson.huang@mediatek.com>