Refuse to create zero area bitmap

Author: erkkah

src/tigr_bitmaps.c

@@ -71,6 +71,9 @@ void tigrResize(Tigr* bmp, int w, int h) {
 }
 
 int tigrCalcScale(int bmpW, int bmpH, int areaW, int areaH) {
+    if (bmpW == 0 || bmpH == 0) {
+        tigrError(0, "Invalid bitmap size, (%dx%d)", bmpW, bmpH);
+    }
     // We want it as big as possible in the window, but still
     // maintaining the correct aspect ratio, and always
     // having an integer pixel size.

tigr.c

@@ -327,6 +327,9 @@ void tigrResize(Tigr* bmp, int w, int h) {
 }
 
 int tigrCalcScale(int bmpW, int bmpH, int areaW, int areaH) {
+    if (bmpW == 0 || bmpH == 0) {
+        tigrError(0, "Invalid bitmap size, (%dx%d)", bmpW, bmpH);
+    }
     // We want it as big as possible in the window, but still
     // maintaining the correct aspect ratio, and always
     // having an integer pixel size.