File renaming may break project layout

Not sure if it's more related to the qmake parser..

Steps to reproduce:

• create a simple project that has at least one header file (e.g. widget app from template)
• remove the empty lines between the HEADERS, SOURCES and FORMS that it looks like this

SOURCES += \
    main.cpp \
    mainwindow.cpp
HEADERS += \
    mainwindow.h
FORMS += \
    mainwindow.ui 

• now rename the header to use a different (valid) C++ header suffix (hpp, H, hh,...)

Current result:

• the file ends up inside the wrong section (inside the pro file it is added to the SOURCES)
• the project tree displays the icon still correct as header

Note: if at least a single empty line is present (before HEADERS and FORMS) this works as expected..

Note: the file will be renamed correctly and files including this file will adapt the include correctly..

Found by Squish test tst_rename_file.