UI: Add missing "#include <QPainterPath>"

[hartwork]

Error was:

g++ -c -pipe -O2 -std=gnu++11 -Wall -Wextra -D_REENTRANT -fPIC -DQT_DEPRECATED_WARNINGS -DQT_NO_DEBUG -DQT_MULTIMEDIA_LIB -DQT_WIDGETS_LIB -DQT_GUI_LIB -DQT_NETWORK_LIB -DQT_CORE_LIB -I. -IUI -I/usr/include/qt5 -I/usr/include/qt5/QtMultimedia -I/usr/include/qt5/QtWidgets -I/usr/include/qt5/QtGui -I/usr/include/qt5/QtNetwork -I/usr/include/qt5/QtCore -I. -I. -I/usr/lib64/qt5/mkspecs/linux-g++ -o WaveFormChunk.o UI/WaveFormChunk.cpp
UI/WaveFormChunk.cpp: In member function ‘void WaveFormChunk::updateWave(Signal*)’:
UI/WaveFormChunk.cpp:61:26: error: aggregate ‘QPainterPath path’ has incomplete type and cannot be defined
   61 |             QPainterPath path;
      |                          ^~~~

[BenPyton]

Thanks!