fix(processrunner): use QChar('\0') to fix CreateProcessW error 87

Replacing char literal '\0' appends with QChar('\0') to ensure the
environment block is built as a proper null-terminated UTF-16 string.
The previous char-literal '\0' was treated as a null pointer constant
by the compiler, producing an invalid environment buffer that caused
CreateProcessW to fail with ERROR_INVALID_PARAMETER (87).

(cherry picked from commit d9ef061)

Author: alphagocc

src/core/processrunner_win.cpp

@@ -238,8 +238,8 @@ ProcessRunnerResult WinProcessRunner::run() {
 	});
 
 	// Need 4 \0 to end the environment string, see CreateProcessW() documentation
-	QString environmentValues =
-	    config.environment.toStringList().join(QChar('\0')) + '\0' + '\0' + '\0' + '\0';
+	QString environmentValues = config.environment.toStringList().join(QChar('\0')) + QChar('\0') +
+	                            QChar('\0') + QChar('\0') + QChar('\0');
 
 	QString commandLine = QString(R"("%1" %2)").arg(config.executableFile).arg(config.arguments);