Check return value of Str... functions

All these functions, StrmyUFgets, StrISgets, etc. can potentially return
NULL. Add a check for it.

file.c

@@ -608,7 +608,7 @@ readHeader(URLFile *uf, Buffer *newBuf, int thru, ParsedURL *pu)
 	if (src)
 	    newBuf->header_source = tmpf;
     }
-    while ((tmp = StrmyUFgets(uf))->length) {
+    while ((tmp = StrmyUFgets(uf)) && tmp->length) {
 #ifdef USE_NNTP
 	if (uf->scheme == SCM_NEWS && tmp->ptr[0] == '.')
 	    Strshrinkfirst(tmp, 1);
@@ -6328,7 +6328,7 @@ file_feed()
 {
     Str s;
     s = StrISgets(_file_lp2);
-    if (s->length == 0) {
+    if (s && s->length == 0) {
 	ISclose(_file_lp2);
 	return NULL;
     }
@@ -7339,7 +7339,7 @@ loadHTMLstream(URLFile *f, Buffer *newBuf, FILE * src, int internal)
 #endif
     if (IStype(f->stream) != IST_ENCODED)
 	f->stream = newEncodedStream(f->stream, f->encoding);
-    while ((lineBuf2 = StrmyUFgets(f))->length) {
+    while ((lineBuf2 = StrmyUFgets(f)) && lineBuf2->length) {
 #ifdef USE_NNTP
 	if (f->scheme == SCM_NEWS && lineBuf2->ptr[0] == '.') {
 	    Strshrinkfirst(lineBuf2, 1);
@@ -7496,7 +7496,7 @@ loadGopherDir0(URLFile *uf, ParsedURL *pu)
 
     pre = 0;
     while (1) {
-	if (lbuf = StrUFgets(uf), lbuf->length == 0)
+	if (!(lbuf = StrUFgets(uf)) || lbuf->length == 0)
 	    break;
 	if (lbuf->ptr[0] == '.' &&
 	    (lbuf->ptr[1] == '\n' || lbuf->ptr[1] == '\r'))
@@ -7666,7 +7666,7 @@ loadBuffer(URLFile *uf, Buffer *volatile newBuf)
     nlines = 0;
     if (IStype(uf->stream) != IST_ENCODED)
 	uf->stream = newEncodedStream(uf->stream, uf->encoding);
-    while ((lineBuf2 = StrmyISgets(uf->stream))->length) {
+    while ((lineBuf2 = StrmyISgets(uf->stream)) && lineBuf2->length) {
 #ifdef USE_NNTP
 	if (uf->scheme == SCM_NEWS && lineBuf2->ptr[0] == '.') {
 	    Strshrinkfirst(lineBuf2, 1);
@@ -8090,7 +8090,8 @@ getNextPage(Buffer *buf, int plen)
 
     init_stream(&uf, SCM_UNKNOWN, NULL);
     for (i = 0; i < plen; i++) {
-	lineBuf2 = StrmyISgets(buf->pagerSource);
+	if (!(lineBuf2 = StrmyISgets(buf->pagerSource)))
+	    return NULL;
 	if (lineBuf2->length == 0) {
 	    /* Assume that `cmd == buf->filename' */
 	    if (buf->filename)

frame.c

@@ -532,7 +532,7 @@ createFrameFile(struct frameset *f, FILE * f1, Buffer *current, int level,
 		    !strcasecmp(frame.body->type, "text/plain")) {
 		    Str tmp;
 		    fprintf(f1, "<pre>\n");
-		    while ((tmp = StrmyUFgets(&f2))->length) {
+		    while ((tmp = StrmyUFgets(&f2)) && tmp->length) {
 			tmp = convertLine(NULL, tmp, HTML_MODE, &charset,
 					  doc_charset);
 			fprintf(f1, "%s", html_quote(tmp->ptr));
@@ -549,7 +549,7 @@ createFrameFile(struct frameset *f, FILE * f1, Buffer *current, int level,
 		    do {
 			if (*p == '\0') {
 			    Str tmp = StrmyUFgets(&f2);
-			    if (tmp->length == 0)
+			    if (!tmp || tmp->length == 0)
 				break;
 			    tmp = convertLine(NULL, tmp, HTML_MODE, &charset,
 					      doc_charset);

ftp.c

@@ -70,7 +70,8 @@ ftp_command(FTP ftp, char *cmd, char *arg, int *status)
     if (!status)
 	return NULL;
     *status = -1;		/* error */
-    tmp = StrISgets(ftp->rf);
+    if (!(tmp = StrISgets(ftp->rf)))
+	return NULL;
     if (IS_DIGIT(tmp->ptr[0]) && IS_DIGIT(tmp->ptr[1]) &&
 	IS_DIGIT(tmp->ptr[2]) && tmp->ptr[3] == ' ')
 	sscanf(tmp->ptr, "%d", status);
@@ -87,7 +88,8 @@ ftp_command(FTP ftp, char *cmd, char *arg, int *status)
      * with the same code, followed immediately by Space <SP>, 
      * optionally some text, and the Telnet end-of-line code. */
     while (1) {
-	tmp = StrISgets(ftp->rf);
+	if (!(tmp = StrISgets(ftp->rf)))
+	    break;
 	if (IS_DIGIT(tmp->ptr[0]) && IS_DIGIT(tmp->ptr[1]) &&
 	    IS_DIGIT(tmp->ptr[2]) && tmp->ptr[3] == ' ') {
 	    sscanf(tmp->ptr, "%d", status);

news.c

@@ -51,7 +51,7 @@ news_command(News * news, char *cmd, char *arg, int *status)
 	return NULL;
     *status = -1;
     tmp = StrISgets(news->rf);
-    if (tmp->length)
+    if (tmp && tmp->length)
 	sscanf(tmp->ptr, "%d", status);
     return tmp;
 }
@@ -396,7 +396,8 @@ loadNewsgroup0(ParsedURL *pu)
     if (status == 224) {
 	f.scheme = SCM_NEWS;
 	while (1) {
-	    tmp = StrISgets(current_news.rf);
+	    if (!(tmp = StrISgets(current_news.rf)))
+		break;
 	    if (NEWS_ENDLINE(tmp->ptr))
 		break;
 	    if (sscanf(tmp->ptr, "%d", &i) != 1)
@@ -474,7 +475,8 @@ loadNewsgroup0(ParsedURL *pu)
     if (status != 215)
 	goto news_end;
     while (1) {
-	tmp = StrISgets(current_news.rf);
+	if (!(tmp = StrISgets(current_news.rf)))
+	    break;
 	if (NEWS_ENDLINE(tmp->ptr))
 	    break;
 	if (flag < 2) {