Only find closest font if system font was not found

Before f951da9 finding a system font used to return early. In order to allow variants, the referenced patch removed the early return so that variants could be applied later. However, there is no need to find the closest font as we already selected the proper system font. This also fixes a bug with setting a custom font handler via RCTSetDefaultFontHandler whos return could get overwritten by the closest font search.

React/Views/RCTFont.mm

@@ -355,16 +355,18 @@ + (UIFont *)updateFont:(UIFont *)font
     }
   }
 
-  // Get the closest font that matches the given weight for the fontFamily
-  CGFloat closestWeight = INFINITY;
-  NSArray<NSString *> *names = fontNamesForFamilyName(familyName);
-  for (NSString *name in names) {
-    UIFont *match = [UIFont fontWithName:name size:fontSize];
-    if (isItalic == isItalicFont(match) && isCondensed == isCondensedFont(match)) {
-      CGFloat testWeight = weightOfFont(match);
-      if (ABS(testWeight - fontWeight) < ABS(closestWeight - fontWeight)) {
-        font = match;
-        closestWeight = testWeight;
+  if (!didFindFont) {
+    // Get the closest font that matches the given weight for the fontFamily
+    CGFloat closestWeight = INFINITY;
+    NSArray<NSString *> *names = fontNamesForFamilyName(familyName);
+    for (NSString *name in names) {
+      UIFont *match = [UIFont fontWithName:name size:fontSize];
+      if (isItalic == isItalicFont(match) && isCondensed == isCondensedFont(match)) {
+        CGFloat testWeight = weightOfFont(match);
+        if (ABS(testWeight - fontWeight) < ABS(closestWeight - fontWeight)) {
+          font = match;
+          closestWeight = testWeight;
+        }
       }
     }
   }