Fix indexing error in isUsedAsInfix

Author: pepeiborra

ghcide/src/Development/IDE/Plugin/Completions/Logic.hs

@@ -636,7 +636,7 @@ isUsedAsInfix line prefixMod prefixText pos
 
 openingBacktick :: T.Text -> T.Text -> T.Text -> Position -> Bool
 openingBacktick line prefixModule prefixText Position { _character }
-  | backtickIndex < 0 = False
+  | backtickIndex < 0 || backtickIndex > T.length line = False
   | otherwise = (line `T.index` backtickIndex) == '`'
     where
     backtickIndex :: Int