DocBook reader: Fix bug with entities in mathphrase element.

Closes #5885.

src/Text/Pandoc/Readers/DocBook.hs

@@ -1109,12 +1109,10 @@ equation e constructor =
       $ filterChildren childPredicate e
       )
 
--- | Get the actual text stored in a verbatim CData block. 'showContent'
+-- | Get the actual text stored in a CData block. 'showContent'
 -- returns the text still surrounded by the [[CDATA]] tags.
---
--- Returns 'showContent' if this is not a verbatim CData
 showVerbatimCData :: Content -> String
-showVerbatimCData (Text (CData CDataVerbatim d _)) = d
+showVerbatimCData (Text (CData _ d _)) = d
 showVerbatimCData c = showContent c
 
 -- | Set the prefix of a name to 'Nothing'

test/command/5885.md

@@ -0,0 +1,20 @@
+```
+% pandoc -f docbook -t latex
+<equation>
+  <mathphrase>
+    J(x, y) = \left\{ \begin{array}{ll}
+    0 &amp; \text{if $I(x, y) &lt; t$} \\
+    1 &amp; \text{if $I(x, y) \ge t$}
+    \end{array}
+    \right.
+  </mathphrase>
+</equation>
+^D
+\[
+    J(x, y) = \left\{ \begin{array}{ll}
+    0 & \text{if $I(x, y) < t$} \\
+    1 & \text{if $I(x, y) \ge t$}
+    \end{array}
+    \right.
+  \]
+```