[ThemeParser] Give a more detailed error when only 7 elements are specified in argb syntax.

Changelog

@@ -1,4 +1,5 @@
 v1.4.3 (dev):
+	- Better error message on invalid argb syntax.
 	- Fix default theme border.
 	- Make '#' in the parser optional.
 	- Update themes.

lexer/theme-lexer.l

@@ -474,6 +474,9 @@ if ( queue == NULL ){
     yylval->colorval.green = rofi_theme_parse_convert_hex(yytext[9],yytext[10]);
     yylval->colorval.blue  = rofi_theme_parse_convert_hex(yytext[11],yytext[12]);
     return T_COLOR;
+}
+<PROPERTIES>argb:{HEX}{7}       {
+    return T_ERROR_ARGB_SPEC;
 }
  /* Color schemes */
 <PROPERTIES>{RGBA}             { return T_COL_RGBA;       }

lexer/theme-parser.y

@@ -155,6 +155,7 @@ static ThemeColor hwb_to_rgb ( double h, double w, double b)
 %token <ival>     T_ERROR_NAMESTRING 4  "invalid element name"
 %token <ival>     T_ERROR_DEFAULTS   5  "invalid defaults name"
 %token <ival>     T_ERROR_INCLUDE    6  "invalid import value"
+%token <ival>     T_ERROR_ARGB_SPEC  7  "invalid argb color. Requires 8 (not 7) elements: argb:AARRGGBB."
 %token <ival>     T_INT                 "Integer number"
 %token <fval>     T_DOUBLE              "Floating-point number"
 %token <sval>     T_STRING              "UTF-8 encoded string"