FileInProjectFinder: Fix findFile() for nonexisting files

The comment above this function says:

 If all fails, it returns the original path
 from the file URL.

That broke with 7b0b4c92cd, which caused the auto
tests in QtSupportPlugin::testQtOutputFormatter
to fail.

Fixes: QTCREATORBUG-21792
Change-Id: I9ed66c86e7a165fe198ee3fcf1bf8b72d850a2d5
Reviewed-by: Orgad Shaneh <orgads@gmail.com>
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

src/libs/utils/fileinprojectfinder.cpp

@@ -144,7 +144,7 @@ QString FileInProjectFinder::findFile(const QUrl &fileUrl, bool *success) const
     if (originalPath.isEmpty()) // e.g. qrc://
         originalPath = fileUrl.path();
 
-    QString result;
+    QString result = originalPath;
     bool found = findFileOrDirectory(originalPath, [&](const QString &fileName, int) {
         result = fileName;
     });