gas gettext warning

gettext("") returns the header entry with meta information, not the
empty string.

	* config/tc-arm.c (reg_expected_msgs[REG_TYPE_RNB]): Don't use
	N_() on empty string.
diff --git a/gas/ChangeLog b/gas/ChangeLog
index 001af54..ddce181 100644
--- a/gas/ChangeLog
+++ b/gas/ChangeLog
@@ -1,5 +1,10 @@
 2020-02-26  Alan Modra  <amodra@gmail.com>
 
+	* config/tc-arm.c (reg_expected_msgs[REG_TYPE_RNB]): Don't use
+	N_() on empty string.
+
+2020-02-26  Alan Modra  <amodra@gmail.com>
+
 	* read.c (read_a_source_file): Call strncpy with length one
 	less than size of original_case_string.
 
diff --git a/gas/config/tc-arm.c b/gas/config/tc-arm.c
index cfbee7e..30c69fb 100644
--- a/gas/config/tc-arm.c
+++ b/gas/config/tc-arm.c
@@ -730,7 +730,7 @@
   [REG_TYPE_MMXWCG] = N_("iWMMXt scalar register expected"),
   [REG_TYPE_XSCALE] = N_("XScale accumulator register expected"),
   [REG_TYPE_MQ]	    = N_("MVE vector register expected"),
-  [REG_TYPE_RNB]    = N_("")
+  [REG_TYPE_RNB]    = ""
 };
 
 /* Some well known registers that we refer to directly elsewhere.  */