[balsheet-pnl] fix: hide Equity sections when not needed

* If currencies are not converted, Unrealized Gains are
meaningless. Hide them.

* If there are no income/expense accounts, retained earnings will be
nil. Remove row.

gnucash/report/standard-reports/balsheet-pnl.scm

@@ -1125,11 +1125,14 @@ also show overall period profit & loss."))
         (add-to-table
          multicol-table-right (_ "Equity")
          (append equity-accounts
-                 (list
-                  (vector (_ "Unrealized Gains")
-                          unrealized-gain-fn)
-                  (vector (_ "Retained Earnings")
-                          retained-earnings-fn)))
+                 (if common-currency
+                     (list (vector (_ "Unrealized Gains")
+                                   unrealized-gain-fn))
+                     '())
+                 (if (null? income-expense)
+                     '()
+                     (list (vector (_ "Retained Earnings")
+                                   retained-earnings-fn))))
          #:negate-amounts? #t)
 
         (if (and common-currency show-rates?)

gnucash/report/standard-reports/test/test-balsheet-pnl.scm

@@ -497,7 +497,7 @@
         "Root.Asset.House" "Total For Asset" "Liability" "Root.Liability"
         "Root.Liability.Bank2" "Root.Liability.Bank2.CreditCard"
         "Root.Liability.Bank2.Loan" "Total For Liability" "Equity" "Root.Equity"
-        "Unrealized Gains" "Retained Earnings" "Total For Equity")
+        "Retained Earnings" "Total For Equity")
       (sxml->table-row-col sxml 1 #f 1))
     (test-equal "default balances"
       '("#200.00" "$106,709.00" "30 FUNDS" "#200.00" "$106,709.00" "30 FUNDS"