TeX reader: fix two bugs.

- Don't crash on array with `\hline` before blank cell.
- Skip whitespace in array column specifier.

See #244.

src/Text/TeXMath/Readers/TeX.hs

@@ -443,19 +443,20 @@ endLineAMS = lexeme $ try $ do
 
 arrayLine :: TP ArrayLine
 arrayLine =
-  sepBy1 (unGrouped <$>
-    manyExp (try (ignorable' *> notFollowedBy (('\n' <$ ctrlseq "end") <|> endLine)) *>
-               expr <*
-               ignorable')) (symbol "&")
-  where ignorable' = ignorable >>
-                     optional (try (ctrlseq "hline" >> ignorable'))
+  sepBy1
+    (ignorable' *>
+      (unGrouped <$>
+        manyExp (try (notFollowedBy (('\n' <$ ctrlseq "end") <|> endLine)) *>
+                   expr <* ignorable'))) (symbol "&")
+  where ignorable' = ignorable >> optional (try (ctrlseq "hline" >> ignorable'))
   -- we don't represent the line, but it shouldn't crash parsing
 
 arrayAlignments :: TP [Alignment]
 arrayAlignments = mconcat <$>
   braces (many (
                 ((:[]) . letterToAlignment <$> letter)
             <|> ([] <$ char '|')
+            <|> ([] <$ oneOf " \t")
             <|> ([] <$ ((char '@' <|> char '!') <* inbraces))
             <|> (do char '*'
                     num <- T.pack <$> braces (many1 digit)

test/regression/244.test

@@ -0,0 +1,13 @@
+<<< tex
+\begin{array}{l cr}
+1 & 2 & 3 \\\hline
+   & 5 & 6 \\
+\end{array}
+>>> native
+[ EArray
+    [ AlignLeft , AlignCenter , AlignRight ]
+    [ [ [ ENumber "1" ] , [ ENumber "2" ] , [ ENumber "3" ] ]
+    , [ [] , [ ENumber "5" ] , [ ENumber "6" ] ]
+    , [ [] ]
+    ]
+]