ignore stray commas in source maps

Author: evanw

code.js

@@ -242,6 +242,12 @@
  continue;
  }
 
+ // Ignore stray commas
+ if (c === 44 /* , */) {
+ i++;
+ continue;
+ }
+
  // Read the generated column
  const generatedColumnDelta = decodeVLQ();
  if (generatedColumnDelta < 0) needToSortGeneratedColumns = true;