fix scanf %c conversion wrongly storing a terminating null byte

this seems to have been a regression from the refactoring which added
the 'm' modifier.

src/stdio/vfscanf.c

@@ -265,8 +265,10 @@ int vfscanf(FILE *restrict f, const char *restrict fmt, va_list ap)
 				if (size == SIZE_l) *(wchar_t **)dest = wcs;
 				else *(char **)dest = s;
 			}
+			if (t != 'c') {
 				if (wcs) wcs[i] = 0;
 				if (s) s[i] = 0;
+			}
 			break;
 		case 'p':
 		case 'X':

src/stdio/vfwscanf.c

@@ -281,8 +281,10 @@ int vfwscanf(FILE *restrict f, const wchar_t *restrict fmt, va_list ap)
 				if (size == SIZE_l) *(wchar_t **)dest = wcs;
 				else *(char **)dest = s;
 			}
+			if (t != 'c') {
 				if (wcs) wcs[i] = 0;
 				if (s) s[i] = 0;
+			}
 			break;
 
 		case 'd': case 'i': case 'o': case 'u': case 'x':