Preserve whitespace between amount and comment for inline maths

In commit 80ad237 ("Preserve whitespace between amount and comment")
we added better handling for whitespace.   Unfortunately, the function
that parses inline maths was not updated accordingly, resulting in this
warning because because $amount->[WHITESPACE] wasn't defined.

    Use of uninitialized value in concatenation (.) or string at ../bin/ledger2beancount line 802.

Fixes #261

bin/ledger2beancount

@@ -1469,13 +1469,14 @@ sub get_default_commodity() {
 sub get_value_expr($) {
     my ($l) = @_;
 
-    if ($l !~ /^(?<math>$RE{balanced}{-parens=>'()'})\s*(?<rest>.*)/) {
+    if ($l !~ /^(?<math>$RE{balanced}{-parens=>'()'})(?<space>\s*)(?<rest>.*)/) {
 	die "Cannot parse inline math from $l\n";
     }
+    my $amount;
     my $math = $+{math};
+    $amount->[WHITESPACE] = $+{space};
     my $rest = $+{rest};
 
-    my $amount;
     $amount->[ADJUST_WHITESPACE] = length($math) - 1; # we subtract the new length later
     # Strip the outer () since beancount doesn't require them.
     $math =~ s/^\(//;

docs/changelog.md

@@ -7,6 +7,7 @@
 * Improve pre-processing example in documentation
 * Add support for amounts with plus sign
 * Set option `name_income` for top-level account `Revenue`
+* Fix whitespace handling for inline maths
 
 ## 2.6 (2021-04-15)
 

tests/amounts.beancount

@@ -28,6 +28,7 @@
 1970-01-01 open Assets:Rewards
 1970-01-01 open Assets:Test
 1970-01-01 open Equity:Exchange
+1970-01-01 open Expenses:Drinks
 1970-01-01 open Expenses:Housing:Rent
 1970-01-01 open Expenses:Travel:Airfare
 1970-01-01 open Income:401k:Match
@@ -290,3 +291,15 @@
   Assets:Test                            1 FOO
   Assets:Test                           -1 FOO
 
+2022-12-02 * "Inline math and whitespace"
+  Expenses:Drinks                 1/1.159 GBP ; comment
+  Assets:Test
+
+2022-12-02 * "Inline math and whitespace"
+  Expenses:Drinks                 1/1.159 GBP; comment
+  Assets:Test
+
+2022-12-02 * "Inline math and whitespace"
+  Expenses:Drinks                 1/1.159 GBP  ; comment
+  Assets:Test
+

tests/amounts.ledger

@@ -263,3 +263,15 @@ commodity $
     Assets:Test                            1
     Assets:Test                           -1
 
+2022-12-02 * Inline math and whitespace
+    Expenses:Drinks                (1/1.159 GBP) ; comment
+    Assets:Test
+
+2022-12-02 * Inline math and whitespace
+    Expenses:Drinks                (1/1.159 GBP); comment
+    Assets:Test
+
+2022-12-02 * Inline math and whitespace
+    Expenses:Drinks                (1/1.159 GBP)  ; comment
+    Assets:Test
+