// See if we just calculated the line number for this FilePos and can use
// that to lookup the start of the line instead of searching for it.
if (LastLineNoFileIDQuery == FID &&
- LastLineNoContentCache->SourceLineCache != 0) {
+ LastLineNoContentCache->SourceLineCache != 0 &&
+ LastLineNoResult < LastLineNoContentCache->NumLines) {
unsigned *SourceLineCache = LastLineNoContentCache->SourceLineCache;
unsigned LineStart = SourceLineCache[LastLineNoResult - 1];
unsigned LineEnd = SourceLineCache[LastLineNoResult];