Debugger: SourceView: Fix several drawing bugs.

- MarkerView: If the view was resized, and the newly revealed region was
after the last source line, it wouldn't be redrawn properly.
- TextView: Reset low color for painting the region after the
source.  Otherwise, if either the instruction pointer or a breakpoint
were at the last line of the current source, the empty space after would
be filled in that color rather than the background color.

src/apps/debugger/user_interface/gui/team_window/SourceView.cpp

@@ -902,9 +902,7 @@ SourceView::MarkerView::Draw(BRect updateRect)
 	// get the lines intersecting with the update rect
 	int32 minLine, maxLine;
 	GetLineRange(updateRect, minLine, maxLine);
-	if (minLine > maxLine)
-		return;
-
+	if (minLine <= maxLine) {
 		// get the markers in that range
 		SourceView::MarkerManager::MarkerList markers;
 		fMarkerManager->GetMarkers(minLine, maxLine, markers);
@@ -940,6 +938,7 @@ SourceView::MarkerView::Draw(BRect updateRect)
 			SetHighColor(fBreakpointOptionMarker);
 			FillEllipse(BPoint(width - 8, y), 2, 2);
 		}
+	}
 
 	float y = (maxLine + 1) * fFontInfo->lineHeight;
 	if (y < updateRect.bottom) {
@@ -1154,6 +1153,7 @@ SourceView::TextView::Draw(BRect updateRect)
 
 	y = (maxLine + 1) * fFontInfo->lineHeight;
 	if (y < updateRect.bottom) {
+		SetLowColor(ui_color(B_DOCUMENT_BACKGROUND_COLOR));
 		FillRect(BRect(0.0, y, Bounds().right, updateRect.bottom),
 			B_SOLID_LOW);
 	}